Which part of the human eye controls the amount of light entering the eye?
Iris
The iris is the coloured, muscular diaphragm behind the cornea. It changes the size of the pupil.
In bright light the iris contracts the pupil to let in less light; in dim light it dilates the pupil to let in more light.
The retina is the light-sensitive screen on which the image forms, the optic nerve carries signals to the brain, and the cornea is the transparent front layer through which light first enters.
Hence, the answer is Iris.
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