Discussion
When a person enters a dark room from bright light, he is not able to see clearly for a little while because the
Answer: C
The Commission's answer is Iris is unable to dilate the pupil immediately.
In bright light the iris keeps the pupil small to limit the light entering the eye. On moving into a dark room, the iris muscles must relax the iris to widen the pupil and let in more light, and this takes a little time, so vision is poor at first. This is the textbook explanation the paper follows. (The retina also takes time to adapt to the dark, which is why full night vision takes much longer.)
The distance between lens and retina never changes; the eye focuses by changing the lens's curvature. The retina does not become insensitive, and 'unable to adjust itself' is too vague to be the reason.
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