Why does it takes sometimes to see objects in a dim room when we enter the room from bright sunligth outside ?

Why does it take some time to see objects in a dim room when you enter the room from bright sunshine outside ?

why does it take some time to see objects in a cinema hall when we just enter the hall from bright sunlight ? Explain in breif?

Why does it take some time to see surroundings clearly in a dark cinema hall when a person enters from bright sunlight?

Why does it sometimes take months for a fracture to heal?

The actor smiled to me when I entered the room as if she knew me.