The size of the pupil of the eye is adjusted by:(a) cornea (b) ciliary muscles (c) optic nerve (d) iris
(d) iris
Explanation
Iris is a flat, coloured (typically brown or blue), ring-shaped membrane behind the cornea of the eye, which controls the amount of light entering the eye by automatically adjusting the size of the pupil according to the intensity of light.
It has two sets of smooth muscles that control the diameter and shape of the pupil, and they are:
1. Sphincter muscle - These muscles are in the shape of a ring located at the edge of the pupil and cause the iris to constrict or contract, reducing the size of the pupil.
If the light is bright, the size of the Pupil gets reduced (smaller), so that less amount of light can enter the eyes.
2. Dilator muscle - These muscles are in the radial shape located radially throughout the iris, like spokes on a wheel, and causes the iris to dilates or stretch, increasing the size of the pupil.
If the light is dim, the size of the Pupil gets increases (larger), so that more amount of light can enter the eyes.
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