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Unfortunately I do not have good background with physics, so I may have missed many points in my question.

But the phenomenon as follow: When I close my room at night I barely see objects in my room (I have very small lamp in my room it's like buttons leds) My led doesn't emerge a strong light which make the room still dark, but after about 30 minute I can see every object in my room very clear.

I don't know why that happen or what is that called, also I don't know what to search about because I'm not physics student.

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    $\begingroup$ Google night adaptation. Your eyes have two types of cells called cones and rods. The cones give you color vision. The rods allow you to essentially see black and white in low light. It takes time for the low light intensity on your retina for your eyes to trigger the chemical changes which your switch eyes from using cones to rods. $\endgroup$ – MaxW Dec 2 '17 at 4:56
  • $\begingroup$ Adding to MaxW answer, the major reason is that the size of your pupil increases in dark allowing more light to enter your eyes. $\endgroup$ – Rishabh Jain Dec 2 '17 at 9:52
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MaxW is correct. When the retina dark-adapts, its sensitivity increases by at least four orders of magnitude, or at least 10,000 times more sensitive. The pupillary response is a much smaller effect and its primary function is to fine tune the eye sensitivity when moving from a more brightly lit environment (i.e. a sunny field) to a less brightly lit environment (i.e. the forest).

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