Номер 5, страница 261 - гдз по физике 9 класс учебник Грачев, Погожев

Физика, 9 класс Учебник, авторы: Грачев Александр Васильевич, Погожев Владимир Александрович, Боков Павел Юрьевич, издательство Вентана-граф, Москва, 2012

Авторы: Грачев А. В., Погожев В. А., Боков П. Ю.

Тип: Учебник

Серия: алгоритм успеха

Издательство: Вентана-граф

Год издания: 2012 - 2026

Цвет обложки: синий изображено здание и радуга

ISBN: 978-5-360-07412-0

Глава 8. Оптика. Параграф 41. Закон отражения света. Упражнения - номер 5, страница 261.

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                            "updated_at" => null
                            "name" => "Вентана-граф"
                            "field_cases" => null
                            "field_translit" => "ventana-graf"
                          ]
                          #original: array:6 [
                            "id" => 5174
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Вентана-граф"
                            "field_cases" => null
                            "field_translit" => "ventana-graf"
                          ]
                          #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 {#1211
                      #items: array:3 [
                        0 => App\Models\Term {#1212
                          #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" => 4180
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Грачев"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Александр"
                            "field_patronymic" => "Васильевич"
                            "field_surname_rp" => null
                          ]
                          #original: array:12 [
                            "id" => 4180
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Грачев"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Александр"
                            "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 {#1213
                          #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" => 5484
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Погожев"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Владимир"
                            "field_patronymic" => "Александрович"
                            "field_surname_rp" => null
                          ]
                          #original: array:12 [
                            "id" => 5484
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Погожев"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Владимир"
                            "field_patronymic" => "Александрович"
                            "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 {#1214
                          #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" => 3888
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Боков"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Павел"
                            "field_patronymic" => "Юрьевич"
                            "field_surname_rp" => null
                          ]
                          #original: array:12 [
                            "id" => 3888
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "Боков"
                            "field_bio" => null
                            "field_degree_rp" => null
                            "field_foreign_lang_name" => null
                            "field_foreign_lang_patronymic" => null
                            "field_foreign_lang_surname" => null
                            "field_name" => "Павел"
                            "field_patronymic" => "Юрьевич"
                            "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 => "*"
                          ]
                        }
                      ]
                      #escapeWhenCastingToString: false
                    }
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1215
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1216
                      #items: array:1 [
                        0 => App\Models\Term {#1217
                          #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 {#1218
                      #items: array:1 [
                        0 => App\Models\Term {#1219
                          #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 {#1220
                      #items: array:1 [
                        0 => App\Models\Term {#1221
                          #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 {#1222
                      #items: array:1 [
                        0 => App\Models\Term {#1223
                          #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" => 4697
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "алгоритм успеха"
                            "field_cases" => null
                            "field_foreign_lang_series" => null
                            "field_transcription_eng" => null
                            "field_translit" => "algoritm uspekha"
                          ]
                          #original: array:8 [
                            "id" => 4697
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "алгоритм успеха"
                            "field_cases" => null
                            "field_foreign_lang_series" => null
                            "field_transcription_eng" => null
                            "field_translit" => "algoritm uspekha"
                          ]
                          #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 {#1224
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1225
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1226
                      #items: array:1 [
                        0 => App\Models\Term {#1227
                          #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" => "2"
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1228
                      #items: array:1 [
                        0 => App\Models\Term {#1229
                          #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" => 6900
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "доработанное"
                            "field_cases" => array:6 [ …6]
                            "field_translit" => "dorabotannoe"
                          ]
                          #original: array:6 [
                            "id" => 6900
                            "created_at" => "2026-04-10 13:58:26"
                            "updated_at" => null
                            "name" => "доработанное"
                            "field_cases" => array:6 [ …6]
                            "field_translit" => "dorabotannoe"
                          ]
                          #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_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1230
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => "изображено здание и радуга"
                    "field_publication_year" => "2012"
                    "field_publication_year_until" => null
                    "field_part" => ""
                    "field_part_writing" => ""
                    "field_second_foreign_language" => null
                    "field_for_whom" => "Учебник для учащихся общеобразовательных организаций"
                    "field_allowed" => null
                    "field_reserve_field" => null
                    "field_link_to_source" => null
                    "field_tasks_count" => "580"
                    "field_priority" => null
                    "field_default_folder" => "/fizika_09/grachev-u/"
                    "field_isbn" => "978-5-360-07412-0"
                    "field_cover" => array:1 [
                      0 => "/media/fizika_09/grachev-u/covers/cover1.webp?ts=1759082140"
                    ]
                    "field_cover_alts" => array:1 [
                      0 => ""
                    ]
                    "field_covers" => array:1 [
                      0 => array:4 [
                        "path" => "/media/fizika_09/grachev-u/covers/cover1.webp?ts=1759082140"
                        "alt" => ""
                        "width" => "2294"
                        "height" => "3039"
                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1231
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1232
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1233
                      #items: []
                      #escapeWhenCastingToString: false
                    }
                    "field_url" => "/9-klass/fizika/grachev-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1234
                      #items: array:1 [
                        0 => App\Models\Term {#1235
                          #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" => 380
                      "subject" => 556
                      "class_subject" => 493
                    ]
                  ]
                  #original: array:50 [
                    "id" => 1202
                    "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 {#1206}
                    "field_class" => Illuminate\Database\Eloquent\Collection {#1207}
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1209}
                    "field_author" => Illuminate\Database\Eloquent\Collection {#1211}
                    "field_author_foreign" => Illuminate\Database\Eloquent\Collection {#1215}
                    "field_book_type" => Illuminate\Database\Eloquent\Collection {#1216}
                    "field_country" => Illuminate\Database\Eloquent\Collection {#1218}
                    "field_city" => Illuminate\Database\Eloquent\Collection {#1220}
                    "field_series" => Illuminate\Database\Eloquent\Collection {#1222}
                    "field_umk" => Illuminate\Database\Eloquent\Collection {#1224}
                    "field_level_of_education" => Illuminate\Database\Eloquent\Collection {#1225}
                    "field_standart_of_education" => Illuminate\Database\Eloquent\Collection {#1226}
                    "field_publication_number" => "2"
                    "field_publication_type" => Illuminate\Database\Eloquent\Collection {#1228}
                    "field_under_the_edition" => Illuminate\Database\Eloquent\Collection {#1230}
                    "field_under_the_edition_degree" => null
                    "field_cover_description" => "изображено здание и радуга"
                    "field_publication_year" => "2012"
                    "field_publication_year_until" => null
                    "field_part" => ""
                    "field_part_writing" => ""
                    "field_second_foreign_language" => null
                    "field_for_whom" => "Учебник для учащихся общеобразовательных организаций"
                    "field_allowed" => null
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                    "field_tasks_count" => "580"
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                    "field_default_folder" => "/fizika_09/grachev-u/"
                    "field_isbn" => "978-5-360-07412-0"
                    "field_cover" => array:1 [
                      0 => "/media/fizika_09/grachev-u/covers/cover1.webp?ts=1759082140"
                    ]
                    "field_cover_alts" => array:1 [
                      0 => ""
                    ]
                    "field_covers" => array:1 [
                      0 => array:4 [
                        "path" => "/media/fizika_09/grachev-u/covers/cover1.webp?ts=1759082140"
                        "alt" => ""
                        "width" => "2294"
                        "height" => "3039"
                      ]
                    ]
                    "field_popular_book" => "0"
                    "field_recommended_books" => Illuminate\Database\Eloquent\Collection {#1231}
                    "field_new_book" => Illuminate\Database\Eloquent\Collection {#1232}
                    "field_old_book" => Illuminate\Database\Eloquent\Collection {#1233}
                    "field_url" => "/9-klass/fizika/grachev-uchebnik"
                    "field_cover_color" => Illuminate\Database\Eloquent\Collection {#1234}
                    "field_metatags_title" => null
                    "field_metatags_description" => null
                    "field_h1" => null
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                    "field_description_bottom" => null
                    "breadcrumbs" => array:3 [
                      "class" => 380
                      "subject" => 556
                      "class_subject" => 493
                    ]
                  ]
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                  #attributeCastCache: []
                  #dateFormat: null
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                  #dispatchesEvents: []
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                  #touches: []
                  +timestamps: true
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                  #hidden: []
                  #visible: []
                  #fillable: []
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                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1236
              #items: []
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1437978
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Оптика"
            "field_branch_order" => "8"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1205}
            "field_page_start" => "248"
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            "field_h1" => null
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            "field_branch_cover" => []
            "field_branch_covers" => []
            "book" => Illuminate\Database\Eloquent\Collection {#1238}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1236}
          ]
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          #attributeCastCache: []
          #dateFormat: null
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          #hidden: []
          #visible: []
          #fillable: []
          #guarded: array:1 [
            0 => "*"
          ]
        }
        1 => App\Models\Branch {#1237
          #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" => 1437983
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Закон отражения света"
            "field_branch_order" => "41"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1242
              #items: array:1 [
                0 => App\Models\Term {#1239
                  #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" => "258"
            "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 {#1241
              #items: array:1 [
                0 => App\Models\Book {#1204}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1240
              #items: array:1 [
                0 => App\Models\Branch {#1034}
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1437983
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Закон отражения света"
            "field_branch_order" => "41"
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1242}
            "field_page_start" => "258"
            "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 {#1241}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1240}
          ]
          #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 {#1243
          #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" => 1437985
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Упражнения"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1244
              #items: []
              #escapeWhenCastingToString: false
            }
            "field_page_start" => "261"
            "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 {#1245
              #items: array:1 [
                0 => App\Models\Book {#1204}
              ]
              #escapeWhenCastingToString: false
            }
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1254
              #items: array:1 [
                0 => App\Models\Branch {#1253
                  #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" => 1437983
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Закон отражения света"
                    "field_branch_order" => "41"
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1255 …2}
                    "field_page_start" => "258"
                    "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 {#1256 …2}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1257 …2}
                  ]
                  #original: array:24 [
                    "id" => 1437983
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "field_display_title" => "Закон отражения света"
                    "field_branch_order" => "41"
                    "field_url" => null
                    "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1255 …2}
                    "field_page_start" => "258"
                    "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 {#1256 …2}
                    "branch_parent" => Illuminate\Database\Eloquent\Collection {#1257 …2}
                  ]
                  #changes: []
                  #casts: []
                  #classCastCache: []
                  #attributeCastCache: []
                  #dateFormat: null
                  #appends: []
                  #dispatchesEvents: []
                  #observables: []
                  #relations: []
                  #touches: []
                  +timestamps: true
                  +usesUniqueIds: false
                  #hidden: []
                  #visible: []
                  #fillable: []
                  #guarded: array:1 [
                    0 => "*"
                  ]
                }
              ]
              #escapeWhenCastingToString: false
            }
          ]
          #original: array:24 [
            "id" => 1437985
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "field_display_title" => "Упражнения"
            "field_branch_order" => null
            "field_url" => null
            "field_branch_type" => Illuminate\Database\Eloquent\Collection {#1244}
            "field_page_start" => "261"
            "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 {#1245}
            "branch_parent" => Illuminate\Database\Eloquent\Collection {#1254}
          ]
          #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 {#1183
      #items: array:2 [
        0 => App\Models\Element {#1175
          #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" => 1705306
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1164
              #items: array:1 [
                0 => App\Models\Edition {#1173
                  #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" => 6112
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
                    "field_order" => "1"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1170 …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 {#1171 …2}
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1168 …2}
                    "field_process_formula" => "katex"
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1169 …2}
                    "field_content_source" => null
                  ]
                  #original: array:21 [
                    "id" => 6112
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Условие"
                    "field_order" => "1"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1170 …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 {#1171 …2}
                    "field_comment" => null
                    "field_similar_book" => Illuminate\Database\Eloquent\Collection {#1168 …2}
                    "field_process_formula" => "katex"
                    "field_edition_group" => Illuminate\Database\Eloquent\Collection {#1169 …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" => "1438425"
              "type" => "task"
            ]
            "text" => "<p><strong>*5.</strong> Лучи света от Солнца падают на Землю, образуя с горизонтом угол $30^\circ$. На Земле стоит цилиндрический бак без крышки, стенки которого вертикальны. Высота бака равна 1 м, диаметр его поперечного сечения — 2 м. На дальнем от Солнца верхнем крае бака закреплено маленькое плоское зеркало так, что отражённый от зеркала солнечный луч попадает в центр дна бака. Найдите угол между плоскостью этого зеркала и горизонтом.</p>"
            "img" => array:1 [
              0 => array:5 [
                "name" => "5-1.jpg"
                "alt" => null
                "width" => "488"
                "height" => 178
                "path" => "/media/fizika_09/grachev-u/0-41upr/5-1.webp?ts=1759503195"
              ]
            ]
          ]
          #original: array:7 [
            "id" => 1705306
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1164}
            "task" => array:2 [
              "refs" => "1438425"
              "type" => "task"
            ]
            "text" => "<p><strong>*5.</strong> Лучи света от Солнца падают на Землю, образуя с горизонтом угол $30^\circ$. На Земле стоит цилиндрический бак без крышки, стенки которого вертикальны. Высота бака равна 1 м, диаметр его поперечного сечения — 2 м. На дальнем от Солнца верхнем крае бака закреплено маленькое плоское зеркало так, что отражённый от зеркала солнечный луч попадает в центр дна бака. Найдите угол между плоскостью этого зеркала и горизонтом.</p>"
            "img" => array:1 [
              0 => array:5 [
                "name" => "5-1.jpg"
                "alt" => null
                "width" => "488"
                "height" => 178
                "path" => "/media/fizika_09/grachev-u/0-41upr/5-1.webp?ts=1759503195"
              ]
            ]
          ]
          #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 {#1166
          #connection: "mysql"
          #table: "elements"
          #primaryKey: "id"
          #keyType: "int"
          +incrementing: true
          #with: []
          #withCount: []
          +preventsLazyLoading: false
          #perPage: 15
          +exists: true
          +wasRecentlyCreated: false
          #escapeWhenCastingToString: false
          #attributes: array:6 [
            "id" => 1812990
            "created_at" => "2026-04-10 13:58:26"
            "updated_at" => null
            "edition" => Illuminate\Database\Eloquent\Collection {#1158
              #items: array:1 [
                0 => App\Models\Edition {#1167
                  #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" => 6644
                    "created_at" => "2026-04-10 13:58:26"
                    "updated_at" => null
                    "title" => "Решение"
                    "field_order" => "2"
                    "field_publisher" => Illuminate\Database\Eloquent\Collection {#1163 …2}
                    "field_content_type" => "free"
                    "field_content_mode" => "text"
                    "field_page_content_mode" => ""
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            "text" => "<p><strong>Дано:</strong></p><p>Угол падения солнечных лучей с горизонтом $\alpha = 30^\circ$</p><p>Высота бака $H = 1$ м</p><p>Диаметр бака $D = 2$ м</p><p>Все данные представлены в системе СИ.</p><p>Радиус бака $R = \frac{D}{2} = \frac{2}{2} = 1$ м.</p><p><strong>Найти:</strong></p><p>Угол $\phi$ между плоскостью зеркала и горизонтом.</p><p><strong>Решение:</strong></p><p>Рассмотрим вертикальное сечение цилиндрического бака, проходящее через его диаметр, центр дна и зеркало. В этом сечении задача становится двумерной.</p><p>Пусть точка М — это местоположение зеркала на дальнем от Солнца верхнем крае бака, а точка С — центр дна бака. Солнечные лучи падают слева. Тогда в системе координат, где центр дна C находится в начале (0, 0), точка M будет иметь координаты $(R, H)$.</p><p><strong>1.</strong> Найдем угол, который отраженный луч образует с горизонтом. Отраженный луч направлен из точки M в точку C. Горизонт параллелен дну бака. Рассмотрим прямоугольный треугольник, образованный точкой M, центром дна C и точкой A на краю дна под зеркалом (с координатами $(R, 0)$). В этом треугольнике (MCA) катеты равны высоте бака $\text{H}$ (длина отрезка MA) и радиусу $\text{R}$ (длина отрезка CA). Угол $\beta$ между отраженным лучом (гипотенуза MC) и горизонтом (катет CA) можно найти из соотношения:</p><p>$\tan \beta = \frac{MA}{CA} = \frac{H}{R}$</p><p>Подставим известные значения:</p><p>$\tan \beta = \frac{1 \text{ м}}{1 \text{ м}} = 1$</p><p>Отсюда находим угол $\beta$:</p><p>$\beta = \arctan(1) = 45^\circ$</p><p><strong>2.</strong> Угол падающего солнечного луча с горизонтом по условию равен $\alpha = 30^\circ$.</p><p><strong>3.</strong> Согласно закону отражения света, угол падения равен углу отражения. Эти углы отсчитываются от нормали (перпендикуляра) к поверхности зеркала. Нормаль к зеркалу делит угол между падающим и отраженным лучами пополам.</p><p>В нашем случае падающий луч образует с горизонталью угол $\alpha=30^\circ$, а отраженный луч образует с горизонталью угол $\beta=45^\circ$. Оба луча находятся под горизонтальной линией, проходящей через зеркало.</p><p>Пусть $\theta_N$ — угол, который нормаль к зеркалу образует с горизонталью. Поскольку нормаль является биссектрисой угла между лучами, ее угол с горизонталью будет равен среднему арифметическому углов этих лучей с горизонталью:</p><p>$\theta_N = \frac{\alpha + \beta}{2} = \frac{30^\circ + 45^\circ}{2} = \frac{75^\circ}{2} = 37.5^\circ$</p><p><strong>4.</strong> Угол $\phi$, который плоскость зеркала составляет с горизонтом, и угол $\theta_N$, который нормаль к зеркалу составляет с горизонтом, в сумме дают $90^\circ$, так как плоскость зеркала и его нормаль перпендикулярны друг другу.</p><p>Найдем искомый угол $\phi$:</p><p>$\phi = 90^\circ - \theta_N = 90^\circ - 37.5^\circ = 52.5^\circ$</p><p><strong>Ответ:</strong> $52.5^\circ$.</p>"
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            "text" => "<p><strong>Дано:</strong></p><p>Угол падения солнечных лучей с горизонтом $\alpha = 30^\circ$</p><p>Высота бака $H = 1$ м</p><p>Диаметр бака $D = 2$ м</p><p>Все данные представлены в системе СИ.</p><p>Радиус бака $R = \frac{D}{2} = \frac{2}{2} = 1$ м.</p><p><strong>Найти:</strong></p><p>Угол $\phi$ между плоскостью зеркала и горизонтом.</p><p><strong>Решение:</strong></p><p>Рассмотрим вертикальное сечение цилиндрического бака, проходящее через его диаметр, центр дна и зеркало. В этом сечении задача становится двумерной.</p><p>Пусть точка М — это местоположение зеркала на дальнем от Солнца верхнем крае бака, а точка С — центр дна бака. Солнечные лучи падают слева. Тогда в системе координат, где центр дна C находится в начале (0, 0), точка M будет иметь координаты $(R, H)$.</p><p><strong>1.</strong> Найдем угол, который отраженный луч образует с горизонтом. Отраженный луч направлен из точки M в точку C. Горизонт параллелен дну бака. Рассмотрим прямоугольный треугольник, образованный точкой M, центром дна C и точкой A на краю дна под зеркалом (с координатами $(R, 0)$). В этом треугольнике (MCA) катеты равны высоте бака $\text{H}$ (длина отрезка MA) и радиусу $\text{R}$ (длина отрезка CA). Угол $\beta$ между отраженным лучом (гипотенуза MC) и горизонтом (катет CA) можно найти из соотношения:</p><p>$\tan \beta = \frac{MA}{CA} = \frac{H}{R}$</p><p>Подставим известные значения:</p><p>$\tan \beta = \frac{1 \text{ м}}{1 \text{ м}} = 1$</p><p>Отсюда находим угол $\beta$:</p><p>$\beta = \arctan(1) = 45^\circ$</p><p><strong>2.</strong> Угол падающего солнечного луча с горизонтом по условию равен $\alpha = 30^\circ$.</p><p><strong>3.</strong> Согласно закону отражения света, угол падения равен углу отражения. Эти углы отсчитываются от нормали (перпендикуляра) к поверхности зеркала. Нормаль к зеркалу делит угол между падающим и отраженным лучами пополам.</p><p>В нашем случае падающий луч образует с горизонталью угол $\alpha=30^\circ$, а отраженный луч образует с горизонталью угол $\beta=45^\circ$. Оба луча находятся под горизонтальной линией, проходящей через зеркало.</p><p>Пусть $\theta_N$ — угол, который нормаль к зеркалу образует с горизонталью. Поскольку нормаль является биссектрисой угла между лучами, ее угол с горизонталью будет равен среднему арифметическому углов этих лучей с горизонталью:</p><p>$\theta_N = \frac{\alpha + \beta}{2} = \frac{30^\circ + 45^\circ}{2} = \frac{75^\circ}{2} = 37.5^\circ$</p><p><strong>4.</strong> Угол $\phi$, который плоскость зеркала составляет с горизонтом, и угол $\theta_N$, который нормаль к зеркалу составляет с горизонтом, в сумме дают $90^\circ$, так как плоскость зеркала и его нормаль перпендикулярны друг другу.</p><p>Найдем искомый угол $\phi$:</p><p>$\phi = 90^\circ - \theta_N = 90^\circ - 37.5^\circ = 52.5^\circ$</p><p><strong>Ответ:</strong> $52.5^\circ$.</p>"
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№5 (с. 261)
Условие. №5 (с. 261)
скриншот условия
Физика, 9 класс Учебник, авторы: Грачев Александр Васильевич, Погожев Владимир Александрович, Боков Павел Юрьевич, издательство Вентана-граф, Москва, 2012, страница 261, номер 5, Условие

*5. Лучи света от Солнца падают на Землю, образуя с горизонтом угол $30^\circ$. На Земле стоит цилиндрический бак без крышки, стенки которого вертикальны. Высота бака равна 1 м, диаметр его поперечного сечения — 2 м. На дальнем от Солнца верхнем крае бака закреплено маленькое плоское зеркало так, что отражённый от зеркала солнечный луч попадает в центр дна бака. Найдите угол между плоскостью этого зеркала и горизонтом.

Решение. №5 (с. 261)

Дано:

Угол падения солнечных лучей с горизонтом $\alpha = 30^\circ$

Высота бака $H = 1$ м

Диаметр бака $D = 2$ м

Все данные представлены в системе СИ.

Радиус бака $R = \frac{D}{2} = \frac{2}{2} = 1$ м.

Найти:

Угол $\phi$ между плоскостью зеркала и горизонтом.

Решение:

Рассмотрим вертикальное сечение цилиндрического бака, проходящее через его диаметр, центр дна и зеркало. В этом сечении задача становится двумерной.

Пусть точка М — это местоположение зеркала на дальнем от Солнца верхнем крае бака, а точка С — центр дна бака. Солнечные лучи падают слева. Тогда в системе координат, где центр дна C находится в начале (0, 0), точка M будет иметь координаты $(R, H)$.

1. Найдем угол, который отраженный луч образует с горизонтом. Отраженный луч направлен из точки M в точку C. Горизонт параллелен дну бака. Рассмотрим прямоугольный треугольник, образованный точкой M, центром дна C и точкой A на краю дна под зеркалом (с координатами $(R, 0)$). В этом треугольнике (MCA) катеты равны высоте бака $\text{H}$ (длина отрезка MA) и радиусу $\text{R}$ (длина отрезка CA). Угол $\beta$ между отраженным лучом (гипотенуза MC) и горизонтом (катет CA) можно найти из соотношения:

$\tan \beta = \frac{MA}{CA} = \frac{H}{R}$

Подставим известные значения:

$\tan \beta = \frac{1 \text{ м}}{1 \text{ м}} = 1$

Отсюда находим угол $\beta$:

$\beta = \arctan(1) = 45^\circ$

2. Угол падающего солнечного луча с горизонтом по условию равен $\alpha = 30^\circ$.

3. Согласно закону отражения света, угол падения равен углу отражения. Эти углы отсчитываются от нормали (перпендикуляра) к поверхности зеркала. Нормаль к зеркалу делит угол между падающим и отраженным лучами пополам.

В нашем случае падающий луч образует с горизонталью угол $\alpha=30^\circ$, а отраженный луч образует с горизонталью угол $\beta=45^\circ$. Оба луча находятся под горизонтальной линией, проходящей через зеркало.

Пусть $\theta_N$ — угол, который нормаль к зеркалу образует с горизонталью. Поскольку нормаль является биссектрисой угла между лучами, ее угол с горизонталью будет равен среднему арифметическому углов этих лучей с горизонталью:

$\theta_N = \frac{\alpha + \beta}{2} = \frac{30^\circ + 45^\circ}{2} = \frac{75^\circ}{2} = 37.5^\circ$

4. Угол $\phi$, который плоскость зеркала составляет с горизонтом, и угол $\theta_N$, который нормаль к зеркалу составляет с горизонтом, в сумме дают $90^\circ$, так как плоскость зеркала и его нормаль перпендикулярны друг другу.

Найдем искомый угол $\phi$:

$\phi = 90^\circ - \theta_N = 90^\circ - 37.5^\circ = 52.5^\circ$

Ответ: $52.5^\circ$.

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