SSC Selection Post 2025 PYQ — Question 9

Correct Answer

It expands to allow more light to enter

Explanation

The pupil is the opening in the center of the iris that controls the amount of light entering the eye. In low light or dark conditions, the pupil expands or dilates. This physiological response is controlled by the involuntary contraction of the radial muscles of the iris, regulated by the sympathetic nervous system. By widening, the pupil maximizes the amount of available light that can reach the retina, which enhances our ability to see more clearly in dim environments.

Key Points

In bright light conditions, the opposite reaction occurs, where the circular muscles of the iris contract, causing the pupil to constrict or get smaller to protect the sensitive retina from excess light damage.

The process of adjusting the pupil size to changing light levels is an automatic reflex called the pupillary light reflex.

The change in pupil size alters the aperture of the eye, similar to how a camera lens adjustments control exposure, and it does not involve any alteration in the actual color of the iris or pupil.

Important Questions and Answers

Question: Which part of the eye regulates the size of the pupil?

Answer: The iris, which contains circular and radial muscles, controls the opening and closing of the pupil.

Question: What is the medical term used for the dilation or expansion of the pupil?

Answer: The medical term for the dilation of the pupil is mydriasis, while constriction is termed miosis.