Question

Amount of light entering the eye is controlled by:
A) Iris
B) Cornea
C) Pupil
D) Crystalline lens

Answer 1

Hint: It is the body’s natural reflex to regulate the amount of light entering the eye. When it is dark the eye regulates itself such that a lot of light can enter into it, while when it is very bright in the surroundings, it restricts the amount of light entering the eye.

Complete step by step answer:
The pupil is a hole in the iris (coloured portion of the eyeball) into which light from the surroundings enters our eye. If a lot of light is coming from the surroundings, then the pupil becomes smaller to restrict the amount of light that can enter into our eye. This is because a lot of light entering our eyes can damage the retina and the eye lens.
Also, when it is very dark, the pupil becomes larger (or dilates) to let a large amount of light enter the eye. This helps us to see better in the dark.
This constriction and dilation of the pupil is controlled by the muscles attached to it known as the ciliary and radial muscles.
Therefore, the amount of light entering the eye is controlled by the pupil.

Therefore, the correct option is C) Pupil.

Note:
Students might think that the iris controls the amount of light entering the eye, since it houses the pupil. However, they must remember that the iris is only the coloured portion of the eyeball and pupil is just a hole in it. The iris has got nothing to do with regulating the light entering the eye. However, it must also be said that the ciliary and radial muscles that control the pupil are present behind the iris. However, the main function of light regulation is done by the pupil.