Номер 4, страница 187 - гдз по физике 8 класс учебник Громов, Родина

Физика, 8 класс Учебник, авторы: Громов Сергей Васильевич, Родина Надежда Александровна, Белага Виктория Владимировна, Ломаченков Иван Алексеевич, Панебратцев Юрий Анатольевич, издательство Просвещение, Москва, 2018

Авторы: Громов С. В., Родина Н. А., Белага В. В., Ломаченков И. А., Панебратцев Ю. А.

Тип: Учебник

Серия: классический курс

Издательство: Просвещение

Год издания: 2018 - 2026

Цвет обложки: синий

ISBN: 978-5-09-052825-2

Глава 3. Электрические явления. Параграф 45. Лампа накаливания. Вопросы - номер 4, страница 187.

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                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Просвещение"
                            "field_cases" => null
                            "field_translit" => "prosveschenie"
                          ]
                          #original: array:6 [
                            "id" => 5153
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Просвещение"
                            "field_cases" => null
                            "field_translit" => "prosveschenie"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1135
                      #items: array:5 [
                        0 => App\Models\Term {#1136
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:12 [
                            "id" => 4194
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Громов"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Сергей"
                            "field_patronymic" => "Васильевич"
                            "field_surname_rp" => null
                          ]
                          #original: array:12 [
                            "id" => 4194
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Громов"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Сергей"
                            "field_patronymic" => "Васильевич"
                            "field_surname_rp" => null
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                        1 => App\Models\Term {#1137
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:12 [
                            "id" => 5604
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Родина"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Надежда"
                            "field_patronymic" => "Александровна"
                            "field_surname_rp" => null
                          ]
                          #original: array:12 [
                            "id" => 5604
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Родина"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Надежда"
                            "field_patronymic" => "Александровна"
                            "field_surname_rp" => null
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                        2 => App\Models\Term {#1138
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:12 [
                            "id" => 3824
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Белага"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Виктория"
                            "field_patronymic" => "Владимировна"
                            "field_surname_rp" => null
                          ]
                          #original: array:12 [
                            "id" => 3824
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Белага"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Виктория"
                            "field_patronymic" => "Владимировна"
                            "field_surname_rp" => null
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                        3 => App\Models\Term {#1139
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:12 [
                            "id" => 5014
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Ломаченков"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Иван"
                            "field_patronymic" => "Алексеевич"
                            "field_surname_rp" => null
                          ]
                          #original: array:12 [
                            "id" => 5014
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Ломаченков"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Иван"
                            "field_patronymic" => "Алексеевич"
                            "field_surname_rp" => null
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                        4 => App\Models\Term {#1140
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:12 [
                            "id" => 5412
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Панебратцев"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Юрий"
                            "field_patronymic" => "Анатольевич"
                            "field_surname_rp" => "Панебратцева"
                          ]
                          #original: array:12 [
                            "id" => 5412
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Панебратцев"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Юрий"
                            "field_patronymic" => "Анатольевич"
                            "field_surname_rp" => "Панебратцева"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1141
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1142
                      #items: array:1 [
                        0 => App\Models\Term {#1143
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:10 [
                            "id" => 6671
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Учебник"
                            "field_book_type_foreign" => null
                            "field_cases" => array:6 [ …6]
                            "field_plural_form" => null
                            "field_short_name" => null
                            "field_short_name_foreign" => null
                            "field_translit" => "uchebnik"
                          ]
                          #original: array:10 [
                            "id" => 6671
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Учебник"
                            "field_book_type_foreign" => null
                            "field_cases" => array:6 [ …6]
                            "field_plural_form" => null
                            "field_short_name" => null
                            "field_short_name_foreign" => null
                            "field_translit" => "uchebnik"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1144
                      #items: array:1 [
                        0 => App\Models\Term {#1145
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [
                            "id" => 9
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Россия"
                            "field_cases" => array:6 [ …6]
                            "field_translit" => "rossiya"
                          ]
                          #original: array:6 [
                            "id" => 9
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Россия"
                            "field_cases" => array:6 [ …6]
                            "field_translit" => "rossiya"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1146
                      #items: array:1 [
                        0 => App\Models\Term {#1147
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [
                            "id" => 15
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Москва"
                            "field_cases" => array:6 [ …6]
                            "field_translit" => "moskva"
                          ]
                          #original: array:6 [
                            "id" => 15
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Москва"
                            "field_cases" => array:6 [ …6]
                            "field_translit" => "moskva"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1148
                      #items: array:1 [
                        0 => App\Models\Term {#1149
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:8 [
                            "id" => 4718
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "классический курс"
                            "field_cases" => null
                            "field_foreign_lang_series" => null
                            "field_transcription_eng" => null
                            "field_translit" => "klassicheskiy kurs"
                          ]
                          #original: array:8 [
                            "id" => 4718
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "классический курс"
                            "field_cases" => null
                            "field_foreign_lang_series" => null
                            "field_transcription_eng" => null
                            "field_translit" => "klassicheskiy kurs"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1150
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1151
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1152
                      #items: array:1 [
                        0 => App\Models\Term {#1153
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:10 [
                            "id" => 6706
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "ФГОС (старый)"
                            "field_cases" => array:6 [ …6]
                            "field_color" => null
                            "field_end_year" => "2022"
                            "field_start_year" => "2019"
                            "field_translit" => "fgos-old"
                            "field_type" => null
                          ]
                          #original: array:10 [
                            "id" => 6706
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "ФГОС (старый)"
                            "field_cases" => array:6 [ …6]
                            "field_color" => null
                            "field_end_year" => "2022"
                            "field_start_year" => "2019"
                            "field_translit" => "fgos-old"
                            "field_type" => null
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_publication_number" => null
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1154
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1155
                      #items: array:1 [
                        0 => App\Models\Term {#1140}
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => null
                    "field_publication_year" => "2018"
                    "field_publication_year_until" => null
                    "field_part" => ""
                    "field_part_writing" => ""
                    "field_second_foreign_language" => null
                    "field_for_whom" => "Учебное пособие для общеобразовательных организаций"
                    "field_allowed" => null
                    "field_reserve_field" => null
                    "field_link_to_source" => null
                    "field_tasks_count" => "830"
                    "field_priority" => null
                    "field_default_folder" => "/fizika_08/gromov-u/"
                    "field_isbn" => "978-5-09-052825-2"
                    "field_cover" => array:1 [
                      0 => "/media/fizika_08/gromov-u/covers/cover1.webp?ts=1763397517"
                    ]
                    "field_cover_alts" => array:1 [
                      0 => ""
                    ]
                    "field_covers" => array:1 [
                      0 => array:4 [
                        "path" => "/media/fizika_08/gromov-u/covers/cover1.webp?ts=1763397517"
                        "alt" => ""
                        "width" => "1881"
                        "height" => "2469"
                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1156
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1157
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1158
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_url" => "/8-klass/fizika/gromov-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1159
                      #items: array:1 [
                        0 => App\Models\Term {#1160
                          #connection: "mysql"
                          #table: "terms"
                          #primaryKey: "id"
                          #keyType: "int"
                          +incrementing: false
                          #with: []
                          #withCount: []
                          +preventsLazyLoading: false
                          #perPage: 15
                          +exists: true
                          +wasRecentlyCreated: false
                          #escapeWhenCastingToString: false
                          #attributes: array:6 [
                            "id" => 49
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "синий"
                            "field_cases" => array:6 [ …6]
                            "field_translit" => "siniy"
                          ]
                          #original: array:6 [
                            "id" => 49
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "синий"
                            "field_cases" => array:6 [ …6]
                            "field_translit" => "siniy"
                          ]
                          #changes: []
                          #casts: []
                          #classCastCache: []
                          #attributeCastCache: []
                          #dateFormat: null
                          #appends: []
                          #dispatchesEvents: []
                          #observables: []
                          #relations: []
                          #touches: []
                          +timestamps: true
                          +usesUniqueIds: false
                          #hidden: []
                          #visible: []
                          #fillable: []
                          #guarded: array:1 [
                            0 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
                    "field_description_top" => null
                    "field_description_bottom" => null
                    "breadcrumbs" => array:3 [
                      "class" => 379
                      "subject" => 556
                      "class_subject" => 492
                    ]
                  ]
                  #original: array:50 [
                    "id" => 3654
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_tree_default_status" => "tasks"
                    "field_pages_status" => null
                    "field_subject" => Illuminate\Database\Eloquent\Collection {#1130}
                    "field_class" => Illuminate\Database\Eloquent\Collection {#1131}
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1133}
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1135}
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1141}
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1142}
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1144}
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1146}
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1148}
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1150}
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1151}
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1152}
                    "field_publication_number" => null
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1154}
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1155}
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => null
                    "field_publication_year" => "2018"
                    "field_publication_year_until" => null
                    "field_part" => ""
                    "field_part_writing" => ""
                    "field_second_foreign_language" => null
                    "field_for_whom" => "Учебное пособие для общеобразовательных организаций"
                    "field_allowed" => null
                    "field_reserve_field" => null
                    "field_link_to_source" => null
                    "field_tasks_count" => "830"
                    "field_priority" => null
                    "field_default_folder" => "/fizika_08/gromov-u/"
                    "field_isbn" => "978-5-09-052825-2"
                    "field_cover" => array:1 [
                      0 => "/media/fizika_08/gromov-u/covers/cover1.webp?ts=1763397517"
                    ]
                    "field_cover_alts" => array:1 [
                      0 => ""
                    ]
                    "field_covers" => array:1 [
                      0 => array:4 [
                        "path" => "/media/fizika_08/gromov-u/covers/cover1.webp?ts=1763397517"
                        "alt" => ""
                        "width" => "1881"
                        "height" => "2469"
                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1156}
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1157}
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1158}
                    "field_url" => "/8-klass/fizika/gromov-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1159}
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
                    "field_description_top" => null
                    "field_description_bottom" => null
                    "breadcrumbs" => array:3 [
                      "class" => 379
                      "subject" => 556
                      "class_subject" => 492
                    ]
                  ]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1161
              #items: []
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1612109
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Электрические явления"
            "field_branch_order" => "3"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1129}
            "field_page_start" => "92"
            "field_branch_display" => "0"
            "field_branch_expanded" => "0"
            "field_display_branch_in_title" => "1"
            "field_display_task_interval" => "0"
            "field_display_branch_page" => "1"
            "field_branch_title_in_content" => "0"
            "field_navigation_title" => null
            "field_metatags_title" => null
            "field_metatags_description" => null
            "field_h1" => null
            "field_description_top" => null
            "field_description_bottom" => null
            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1163}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1161}
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
          #observables: []
          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        1 => App\Models\Branch {#1162
          #connection: "mysql"
          #table: "branches"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:24 [
            "id" => 1612178
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Лампа накаливания"
            "field_branch_order" => "45"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1167
              #items: array:1 [
                0 => App\Models\Term {#1164
                  #connection: "mysql"
                  #table: "terms"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:7 [
                    "id" => 32
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Параграф"
                    "field_cases" => array:6 [ …6]
                    "field_page_check_not_needed" => null
                    "field_short_name" => "§"
                  ]
                  #original: array:7 [
                    "id" => 32
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "name" => "Параграф"
                    "field_cases" => array:6 [ …6]
                    "field_page_check_not_needed" => null
                    "field_short_name" => "§"
                  ]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "183"
            "field_branch_display" => "0"
            "field_branch_expanded" => "0"
            "field_display_branch_in_title" => "1"
            "field_display_task_interval" => "0"
            "field_display_branch_page" => "1"
            "field_branch_title_in_content" => "0"
            "field_navigation_title" => null
            "field_metatags_title" => null
            "field_metatags_description" => null
            "field_h1" => null
            "field_description_top" => null
            "field_description_bottom" => null
            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1166
              #items: array:1 [
                0 => App\Models\Book {#1128}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1165
              #items: array:1 [
                0 => App\Models\Branch {#1034}
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1612178
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Лампа накаливания"
            "field_branch_order" => "45"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1167}
            "field_page_start" => "183"
            "field_branch_display" => "0"
            "field_branch_expanded" => "0"
            "field_display_branch_in_title" => "1"
            "field_display_task_interval" => "0"
            "field_display_branch_page" => "1"
            "field_branch_title_in_content" => "0"
            "field_navigation_title" => null
            "field_metatags_title" => null
            "field_metatags_description" => null
            "field_h1" => null
            "field_description_top" => null
            "field_description_bottom" => null
            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1166}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1165}
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
          #observables: []
          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        2 => App\Models\Branch {#1168
          #connection: "mysql"
          #table: "branches"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:24 [
            "id" => 1612180
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Вопросы"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1169
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "187"
            "field_branch_display" => "0"
            "field_branch_expanded" => "0"
            "field_display_branch_in_title" => "1"
            "field_display_task_interval" => "0"
            "field_display_branch_page" => "1"
            "field_branch_title_in_content" => "0"
            "field_navigation_title" => null
            "field_metatags_title" => null
            "field_metatags_description" => null
            "field_h1" => null
            "field_description_top" => null
            "field_description_bottom" => null
            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1170
              #items: array:1 [
                0 => App\Models\Book {#1128}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1179
              #items: array:1 [
                0 => App\Models\Branch {#1178
                  #connection: "mysql"
                  #table: "branches"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: true
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:24 [
                    "id" => 1612178
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Лампа накаливания"
                    "field_branch_order" => "45"
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1180 …2}
                    "field_page_start" => "183"
                    "field_branch_display" => "0"
                    "field_branch_expanded" => "0"
                    "field_display_branch_in_title" => "1"
                    "field_display_task_interval" => "0"
                    "field_display_branch_page" => "1"
                    "field_branch_title_in_content" => "0"
                    "field_navigation_title" => null
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
                    "field_description_top" => null
                    "field_description_bottom" => null
                    "field_branch_cover" => []
                    "field_branch_covers" => []
                    "book" => Illuminate\Database\Eloquent\Collection {#1181 …2}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1182 …2}
                  ]
                  #original: array:24 [
                    "id" => 1612178
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Лампа накаливания"
                    "field_branch_order" => "45"
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1180 …2}
                    "field_page_start" => "183"
                    "field_branch_display" => "0"
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                    "field_display_branch_page" => "1"
                    "field_branch_title_in_content" => "0"
                    "field_navigation_title" => null
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
                    "field_description_top" => null
                    "field_description_bottom" => null
                    "field_branch_cover" => []
                    "field_branch_covers" => []
                    "book" => Illuminate\Database\Eloquent\Collection {#1181 …2}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1182 …2}
                  ]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
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                  #dispatchesEvents: []
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                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1612180
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Вопросы"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1169}
            "field_page_start" => "187"
            "field_branch_display" => "0"
            "field_branch_expanded" => "0"
            "field_display_branch_in_title" => "1"
            "field_display_task_interval" => "0"
            "field_display_branch_page" => "1"
            "field_branch_title_in_content" => "0"
            "field_navigation_title" => null
            "field_metatags_title" => null
            "field_metatags_description" => null
            "field_h1" => null
            "field_description_top" => null
            "field_description_bottom" => null
            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1170}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1179}
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
          #observables: []
          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
      ]
      #escapeWhenCastingToString: false
    }
    "content" => Illuminate\Database\Eloquent\Collection {#1075
      #items: array:2 [
        0 => App\Models\Element {#1107
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:7 [
            "id" => 1850393
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1098
              #items: array:1 [
                0 => App\Models\Edition {#1092
                  #connection: "mysql"
                  #table: "editions"
                  #primaryKey: "id"
                  #keyType: "int"
                  +incrementing: false
                  #with: []
                  #withCount: []
                  +preventsLazyLoading: false
                  #perPage: 15
                  +exists: true
                  +wasRecentlyCreated: false
                  #escapeWhenCastingToString: false
                  #attributes: array:21 [
                    "id" => 6892
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
                    "field_order" => "1"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1104 …2}
                    "field_content_type" => "free"
                    "field_content_mode" => "text, image"
                    "field_page_content_mode" => "image"
                    "field_content_text_checked" => "0"
                    "field_page_content_text_checked" => "0"
                    "field_solution_author" => "Автор"
                    "field_moderator" => "stas"
                    "field_edition_type" => "statement"
                    "field_root_dir" => "0-"
                    "field_responsible" => Illuminate\Database\Eloquent\Collection {#1105 …2}
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1103 …2}
                    "field_process_formula" => "katex"
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1102 …2}
                    "field_content_source" => null
                  ]
                  #original: array:21 [
                    "id" => 6892
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
                    "field_order" => "1"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1104 …2}
                    "field_content_type" => "free"
                    "field_content_mode" => "text, image"
                    "field_page_content_mode" => "image"
                    "field_content_text_checked" => "0"
                    "field_page_content_text_checked" => "0"
                    "field_solution_author" => "Автор"
                    "field_moderator" => "stas"
                    "field_edition_type" => "statement"
                    "field_root_dir" => "0-"
                    "field_responsible" => Illuminate\Database\Eloquent\Collection {#1105 …2}
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1103 …2}
                    "field_process_formula" => "katex"
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1102 …2}
                    "field_content_source" => null
                  ]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "task" => array:2 [
              "refs" => "1612679"
              "type" => "task"
            ]
            "text" => "<p><strong>4.</strong> Выведите формулу (45.1).</p>"
            "img" => array:1 [
              0 => array:5 [
                "name" => "4-1.jpg"
                "alt" => null
                "width" => "675"
                "height" => 113
                "path" => "/media/fizika_08/gromov-u/0-45vopr/4-1.webp?ts=1763477967"
              ]
            ]
          ]
          #original: array:7 [
            "id" => 1850393
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1098}
            "task" => array:2 [
              "refs" => "1612679"
              "type" => "task"
            ]
            "text" => "<p><strong>4.</strong> Выведите формулу (45.1).</p>"
            "img" => array:1 [
              0 => array:5 [
                "name" => "4-1.jpg"
                "alt" => null
                "width" => "675"
                "height" => 113
                "path" => "/media/fizika_08/gromov-u/0-45vopr/4-1.webp?ts=1763477967"
              ]
            ]
          ]
          #changes: []
          #casts: []
          #classCastCache: []
          #attributeCastCache: []
          #dateFormat: null
          #appends: []
          #dispatchesEvents: []
          #observables: []
          #relations: []
          #touches: []
          +timestamps: true
          +usesUniqueIds: false
          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        1 => App\Models\Element {#1100
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
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            "text" => "<p><strong>4.</strong> Выведите формулу (45.1).</p><p>Предполагается, что формула (45.1) — это формула для релятивистского эффекта Доплера. Ниже представлен ее вывод.</p><p><strong>Дано:</strong></p><p>$\nu_0$ - частота электромагнитной волны в системе отсчета, связанной с источником (собственная частота);</p><p>$\text{v}$ - скорость источника относительно наблюдателя;</p><p>$\text{c}$ - скорость света в вакууме;</p><p>$\theta$ - угол между вектором скорости источника $\vec{v}$ и направлением на наблюдателя (в системе отсчета наблюдателя).</p><p><strong>Найти:</strong></p><p>$\nu$ - частота волны, которую регистрирует наблюдатель.</p><p><strong>Решение:</strong></p><p>Вывод формулы основан на специальной теории относительности. Рассмотрим две инерциальные системы отсчета: $\text{S}$, в которой наблюдатель покоится, и $S'$, в которой покоится источник. Пусть система $S'$ движется со скоростью $\vec{v}$ относительно системы $\text{S}$.</p><p>Пусть источник в своей системе отсчета $S'$ испускает два последовательных максимума (гребня) волны в моменты времени $t'_1 = 0$ и $t'_2 = T_0$, где $T_0 = 1/\nu_0$ - период колебаний в системе отсчета источника (собственный период). Будем считать, что в оба момента времени источник находится в начале координат системы $S'$, то есть его пространственные координаты равны нулю.</p><p>Найдем, в какие моменты времени и в каких точках системы отсчета $\text{S}$ происходят эти два события. Для этого воспользуемся преобразованиями Лоренца. Будем считать, что оси $\text{x}$ и $x'$ совпадают и направлены вдоль вектора скорости $\vec{v}$, а в момент $t = t' = 0$ начала координат систем совпадали.</p><p>Преобразования Лоренца для времени имеют вид: $t = \gamma (t' + \frac{vx'}{c^2})$, где $\gamma = \frac{1}{\sqrt{1 - v^2/c^2}}$ - фактор Лоренца.</p><p>Для первого события (испускание первого гребня, $t'_1 = 0$, $x'_1=0$):</p><p>$t_1 = \gamma (0 + \frac{v \cdot 0}{c^2}) = 0$.</p><p>Положение источника в этот момент в системе $\text{S}$ - начало координат, $\vec{r}_1 = (0, 0, 0)$.</p><p>Для второго события (испускание второго гребня, $t'_2 = T_0$, $x'_2=0$):</p><p>$t_2 = \gamma (T_0 + \frac{v \cdot 0}{c^2}) = \gamma T_0$.</p><p>За это время $t_2$ источник в системе $\text{S}$ переместился в точку с радиус-вектором $\vec{r}_2 = \vec{v}t_2 = \vec{v}\gamma T_0$.</p><p>Теперь определим моменты времени, когда эти два гребня волны достигнут наблюдателя, находящегося в системе $\text{S}$ в точке с радиус-вектором $\vec{R}$. Будем считать, что наблюдатель находится очень далеко от источника, так что $R \gg |\vec{r}_2|$.</p><p>Первый гребень, испущенный из точки $\vec{r}_1=0$ в момент $t_1=0$, прибудет к наблюдателю в момент времени:</p><p>$t_{obs,1} = t_1 + \frac{|\vec{R}-\vec{r}_1|}{c} = 0 + \frac{R}{c} = \frac{R}{c}$.</p><p>Второй гребень, испущенный из точки $\vec{r}_2$ в момент $t_2$, прибудет к наблюдателю в момент времени:</p><p>$t_{obs,2} = t_2 + \frac{|\vec{R}-\vec{r}_2|}{c}$.</p><p>Поскольку $\text{R}$ велико, можно считать, что лучи, идущие к наблюдателю, параллельны. Тогда расстояние $|\vec{R}-\vec{r}_2|$ можно аппроксимировать как $R - \vec{n} \cdot \vec{r}_2$, где $\vec{n} = \vec{R}/R$ - единичный вектор в направлении на наблюдателя. Тогда:</p><p>$t_{obs,2} \approx t_2 + \frac{R - \vec{n} \cdot \vec{r}_2}{c} = \gamma T_0 + \frac{R - \vec{n} \cdot (\vec{v}\gamma T_0)}{c} = \gamma T_0 + \frac{R}{c} - \frac{\gamma T_0 (\vec{v} \cdot \vec{n})}{c}$.</p><p>Период $\text{T}$, измеряемый наблюдателем, равен разности времен прихода двух последовательных гребней:</p><p>$T = t_{obs,2} - t_{obs,1} = \left(\gamma T_0 + \frac{R}{c} - \frac{\gamma T_0 (\vec{v} \cdot \vec{n})}{c}\right) - \frac{R}{c} = \gamma T_0 \left(1 - \frac{\vec{v} \cdot \vec{n}}{c}\right)$.</p><p>Скалярное произведение $\vec{v} \cdot \vec{n} = v \cdot 1 \cdot \cos\theta = v\cos\theta$, где $\theta$ - угол между вектором скорости источника $\vec{v}$ и направлением на наблюдателя $\vec{n}$.</p><p>Таким образом, $T = \gamma T_0 \left(1 - \frac{v\cos\theta}{c}\right)$.</p><p>Частота $\nu$, регистрируемая наблюдателем, равна $\nu = 1/T$. Собственная частота источника $\nu_0 = 1/T_0$. Подставляя эти соотношения, получаем:</p><p>$\nu = \frac{1}{\gamma T_0 \left(1 - \frac{v\cos\theta}{c}\right)} = \frac{\nu_0}{\gamma \left(1 - \frac{v\cos\theta}{c}\right)}$.</p><p>Наконец, подставим выражение для фактора Лоренца $\gamma = \frac{1}{\sqrt{1 - v^2/c^2}}$:</p><p>$\nu = \nu_0 \frac{\sqrt{1 - v^2/c^2}}{1 - \frac{v}{c}\cos\theta}$.</p><p>Это и есть искомая формула релятивистского эффекта Доплера.</p><p><strong>Ответ:</strong></p><p>Формула релятивистского эффекта Доплера, связывающая частоту $\nu_0$, испускаемую источником в его системе отсчета, с частотой $\nu$, принимаемой наблюдателем в своей системе отсчета, имеет вид:</p><p>$\nu = \nu_0 \frac{\sqrt{1 - v^2/c^2}}{1 - \frac{v}{c}\cos\theta}$</p><p>где $\text{v}$ - скорость источника относительно наблюдателя, $\text{c}$ - скорость света, $\theta$ - угол между вектором скорости источника и направлением от источника к наблюдателю, измеренный в системе отсчета наблюдателя.</p>"
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            "text" => "<p><strong>4.</strong> Выведите формулу (45.1).</p><p>Предполагается, что формула (45.1) — это формула для релятивистского эффекта Доплера. Ниже представлен ее вывод.</p><p><strong>Дано:</strong></p><p>$\nu_0$ - частота электромагнитной волны в системе отсчета, связанной с источником (собственная частота);</p><p>$\text{v}$ - скорость источника относительно наблюдателя;</p><p>$\text{c}$ - скорость света в вакууме;</p><p>$\theta$ - угол между вектором скорости источника $\vec{v}$ и направлением на наблюдателя (в системе отсчета наблюдателя).</p><p><strong>Найти:</strong></p><p>$\nu$ - частота волны, которую регистрирует наблюдатель.</p><p><strong>Решение:</strong></p><p>Вывод формулы основан на специальной теории относительности. Рассмотрим две инерциальные системы отсчета: $\text{S}$, в которой наблюдатель покоится, и $S'$, в которой покоится источник. Пусть система $S'$ движется со скоростью $\vec{v}$ относительно системы $\text{S}$.</p><p>Пусть источник в своей системе отсчета $S'$ испускает два последовательных максимума (гребня) волны в моменты времени $t'_1 = 0$ и $t'_2 = T_0$, где $T_0 = 1/\nu_0$ - период колебаний в системе отсчета источника (собственный период). Будем считать, что в оба момента времени источник находится в начале координат системы $S'$, то есть его пространственные координаты равны нулю.</p><p>Найдем, в какие моменты времени и в каких точках системы отсчета $\text{S}$ происходят эти два события. Для этого воспользуемся преобразованиями Лоренца. Будем считать, что оси $\text{x}$ и $x'$ совпадают и направлены вдоль вектора скорости $\vec{v}$, а в момент $t = t' = 0$ начала координат систем совпадали.</p><p>Преобразования Лоренца для времени имеют вид: $t = \gamma (t' + \frac{vx'}{c^2})$, где $\gamma = \frac{1}{\sqrt{1 - v^2/c^2}}$ - фактор Лоренца.</p><p>Для первого события (испускание первого гребня, $t'_1 = 0$, $x'_1=0$):</p><p>$t_1 = \gamma (0 + \frac{v \cdot 0}{c^2}) = 0$.</p><p>Положение источника в этот момент в системе $\text{S}$ - начало координат, $\vec{r}_1 = (0, 0, 0)$.</p><p>Для второго события (испускание второго гребня, $t'_2 = T_0$, $x'_2=0$):</p><p>$t_2 = \gamma (T_0 + \frac{v \cdot 0}{c^2}) = \gamma T_0$.</p><p>За это время $t_2$ источник в системе $\text{S}$ переместился в точку с радиус-вектором $\vec{r}_2 = \vec{v}t_2 = \vec{v}\gamma T_0$.</p><p>Теперь определим моменты времени, когда эти два гребня волны достигнут наблюдателя, находящегося в системе $\text{S}$ в точке с радиус-вектором $\vec{R}$. Будем считать, что наблюдатель находится очень далеко от источника, так что $R \gg |\vec{r}_2|$.</p><p>Первый гребень, испущенный из точки $\vec{r}_1=0$ в момент $t_1=0$, прибудет к наблюдателю в момент времени:</p><p>$t_{obs,1} = t_1 + \frac{|\vec{R}-\vec{r}_1|}{c} = 0 + \frac{R}{c} = \frac{R}{c}$.</p><p>Второй гребень, испущенный из точки $\vec{r}_2$ в момент $t_2$, прибудет к наблюдателю в момент времени:</p><p>$t_{obs,2} = t_2 + \frac{|\vec{R}-\vec{r}_2|}{c}$.</p><p>Поскольку $\text{R}$ велико, можно считать, что лучи, идущие к наблюдателю, параллельны. Тогда расстояние $|\vec{R}-\vec{r}_2|$ можно аппроксимировать как $R - \vec{n} \cdot \vec{r}_2$, где $\vec{n} = \vec{R}/R$ - единичный вектор в направлении на наблюдателя. Тогда:</p><p>$t_{obs,2} \approx t_2 + \frac{R - \vec{n} \cdot \vec{r}_2}{c} = \gamma T_0 + \frac{R - \vec{n} \cdot (\vec{v}\gamma T_0)}{c} = \gamma T_0 + \frac{R}{c} - \frac{\gamma T_0 (\vec{v} \cdot \vec{n})}{c}$.</p><p>Период $\text{T}$, измеряемый наблюдателем, равен разности времен прихода двух последовательных гребней:</p><p>$T = t_{obs,2} - t_{obs,1} = \left(\gamma T_0 + \frac{R}{c} - \frac{\gamma T_0 (\vec{v} \cdot \vec{n})}{c}\right) - \frac{R}{c} = \gamma T_0 \left(1 - \frac{\vec{v} \cdot \vec{n}}{c}\right)$.</p><p>Скалярное произведение $\vec{v} \cdot \vec{n} = v \cdot 1 \cdot \cos\theta = v\cos\theta$, где $\theta$ - угол между вектором скорости источника $\vec{v}$ и направлением на наблюдателя $\vec{n}$.</p><p>Таким образом, $T = \gamma T_0 \left(1 - \frac{v\cos\theta}{c}\right)$.</p><p>Частота $\nu$, регистрируемая наблюдателем, равна $\nu = 1/T$. Собственная частота источника $\nu_0 = 1/T_0$. Подставляя эти соотношения, получаем:</p><p>$\nu = \frac{1}{\gamma T_0 \left(1 - \frac{v\cos\theta}{c}\right)} = \frac{\nu_0}{\gamma \left(1 - \frac{v\cos\theta}{c}\right)}$.</p><p>Наконец, подставим выражение для фактора Лоренца $\gamma = \frac{1}{\sqrt{1 - v^2/c^2}}$:</p><p>$\nu = \nu_0 \frac{\sqrt{1 - v^2/c^2}}{1 - \frac{v}{c}\cos\theta}$.</p><p>Это и есть искомая формула релятивистского эффекта Доплера.</p><p><strong>Ответ:</strong></p><p>Формула релятивистского эффекта Доплера, связывающая частоту $\nu_0$, испускаемую источником в его системе отсчета, с частотой $\nu$, принимаемой наблюдателем в своей системе отсчета, имеет вид:</p><p>$\nu = \nu_0 \frac{\sqrt{1 - v^2/c^2}}{1 - \frac{v}{c}\cos\theta}$</p><p>где $\text{v}$ - скорость источника относительно наблюдателя, $\text{c}$ - скорость света, $\theta$ - угол между вектором скорости источника и направлением от источника к наблюдателю, измеренный в системе отсчета наблюдателя.</p>"
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№4 (с. 187)
Условие. №4 (с. 187)
скриншот условия
Физика, 8 класс Учебник, авторы: Громов Сергей Васильевич, Родина Надежда Александровна, Белага Виктория Владимировна, Ломаченков Иван Алексеевич, Панебратцев Юрий Анатольевич, издательство Просвещение, Москва, 2018, страница 187, номер 4, Условие

4. Выведите формулу (45.1).

Решение. №4 (с. 187)

4. Выведите формулу (45.1).

Предполагается, что формула (45.1) — это формула для релятивистского эффекта Доплера. Ниже представлен ее вывод.

Дано:

$\nu_0$ - частота электромагнитной волны в системе отсчета, связанной с источником (собственная частота);

$\text{v}$ - скорость источника относительно наблюдателя;

$\text{c}$ - скорость света в вакууме;

$\theta$ - угол между вектором скорости источника $\vec{v}$ и направлением на наблюдателя (в системе отсчета наблюдателя).

Найти:

$\nu$ - частота волны, которую регистрирует наблюдатель.

Решение:

Вывод формулы основан на специальной теории относительности. Рассмотрим две инерциальные системы отсчета: $\text{S}$, в которой наблюдатель покоится, и $S'$, в которой покоится источник. Пусть система $S'$ движется со скоростью $\vec{v}$ относительно системы $\text{S}$.

Пусть источник в своей системе отсчета $S'$ испускает два последовательных максимума (гребня) волны в моменты времени $t'_1 = 0$ и $t'_2 = T_0$, где $T_0 = 1/\nu_0$ - период колебаний в системе отсчета источника (собственный период). Будем считать, что в оба момента времени источник находится в начале координат системы $S'$, то есть его пространственные координаты равны нулю.

Найдем, в какие моменты времени и в каких точках системы отсчета $\text{S}$ происходят эти два события. Для этого воспользуемся преобразованиями Лоренца. Будем считать, что оси $\text{x}$ и $x'$ совпадают и направлены вдоль вектора скорости $\vec{v}$, а в момент $t = t' = 0$ начала координат систем совпадали.

Преобразования Лоренца для времени имеют вид: $t = \gamma (t' + \frac{vx'}{c^2})$, где $\gamma = \frac{1}{\sqrt{1 - v^2/c^2}}$ - фактор Лоренца.

Для первого события (испускание первого гребня, $t'_1 = 0$, $x'_1=0$):

$t_1 = \gamma (0 + \frac{v \cdot 0}{c^2}) = 0$.

Положение источника в этот момент в системе $\text{S}$ - начало координат, $\vec{r}_1 = (0, 0, 0)$.

Для второго события (испускание второго гребня, $t'_2 = T_0$, $x'_2=0$):

$t_2 = \gamma (T_0 + \frac{v \cdot 0}{c^2}) = \gamma T_0$.

За это время $t_2$ источник в системе $\text{S}$ переместился в точку с радиус-вектором $\vec{r}_2 = \vec{v}t_2 = \vec{v}\gamma T_0$.

Теперь определим моменты времени, когда эти два гребня волны достигнут наблюдателя, находящегося в системе $\text{S}$ в точке с радиус-вектором $\vec{R}$. Будем считать, что наблюдатель находится очень далеко от источника, так что $R \gg |\vec{r}_2|$.

Первый гребень, испущенный из точки $\vec{r}_1=0$ в момент $t_1=0$, прибудет к наблюдателю в момент времени:

$t_{obs,1} = t_1 + \frac{|\vec{R}-\vec{r}_1|}{c} = 0 + \frac{R}{c} = \frac{R}{c}$.

Второй гребень, испущенный из точки $\vec{r}_2$ в момент $t_2$, прибудет к наблюдателю в момент времени:

$t_{obs,2} = t_2 + \frac{|\vec{R}-\vec{r}_2|}{c}$.

Поскольку $\text{R}$ велико, можно считать, что лучи, идущие к наблюдателю, параллельны. Тогда расстояние $|\vec{R}-\vec{r}_2|$ можно аппроксимировать как $R - \vec{n} \cdot \vec{r}_2$, где $\vec{n} = \vec{R}/R$ - единичный вектор в направлении на наблюдателя. Тогда:

$t_{obs,2} \approx t_2 + \frac{R - \vec{n} \cdot \vec{r}_2}{c} = \gamma T_0 + \frac{R - \vec{n} \cdot (\vec{v}\gamma T_0)}{c} = \gamma T_0 + \frac{R}{c} - \frac{\gamma T_0 (\vec{v} \cdot \vec{n})}{c}$.

Период $\text{T}$, измеряемый наблюдателем, равен разности времен прихода двух последовательных гребней:

$T = t_{obs,2} - t_{obs,1} = \left(\gamma T_0 + \frac{R}{c} - \frac{\gamma T_0 (\vec{v} \cdot \vec{n})}{c}\right) - \frac{R}{c} = \gamma T_0 \left(1 - \frac{\vec{v} \cdot \vec{n}}{c}\right)$.

Скалярное произведение $\vec{v} \cdot \vec{n} = v \cdot 1 \cdot \cos\theta = v\cos\theta$, где $\theta$ - угол между вектором скорости источника $\vec{v}$ и направлением на наблюдателя $\vec{n}$.

Таким образом, $T = \gamma T_0 \left(1 - \frac{v\cos\theta}{c}\right)$.

Частота $\nu$, регистрируемая наблюдателем, равна $\nu = 1/T$. Собственная частота источника $\nu_0 = 1/T_0$. Подставляя эти соотношения, получаем:

$\nu = \frac{1}{\gamma T_0 \left(1 - \frac{v\cos\theta}{c}\right)} = \frac{\nu_0}{\gamma \left(1 - \frac{v\cos\theta}{c}\right)}$.

Наконец, подставим выражение для фактора Лоренца $\gamma = \frac{1}{\sqrt{1 - v^2/c^2}}$:

$\nu = \nu_0 \frac{\sqrt{1 - v^2/c^2}}{1 - \frac{v}{c}\cos\theta}$.

Это и есть искомая формула релятивистского эффекта Доплера.

Ответ:

Формула релятивистского эффекта Доплера, связывающая частоту $\nu_0$, испускаемую источником в его системе отсчета, с частотой $\nu$, принимаемой наблюдателем в своей системе отсчета, имеет вид:

$\nu = \nu_0 \frac{\sqrt{1 - v^2/c^2}}{1 - \frac{v}{c}\cos\theta}$

где $\text{v}$ - скорость источника относительно наблюдателя, $\text{c}$ - скорость света, $\theta$ - угол между вектором скорости источника и направлением от источника к наблюдателю, измеренный в системе отсчета наблюдателя.

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