Question

The amount of light entering the eye is regulated and controlled by the

• A. pupil
• B. optical nerve
• C. retina
• D. ciliary muscles

Hint:

Think of the pupil as the aperture of a camera; it adjusts in size to control the amount of light passing through to the sensor (retina).

Answer 1

The Correct Option is A

Step 1: Understand the function of different parts of the eye related to light entry.

• 
  Pupil:
  The pupil is the opening in the center of the iris that allows light to enter the eye. Its size is adjusted by the iris muscles to control the amount of light reaching the retina. In bright light, the pupil constricts (becomes smaller) to limit the amount of light, and in dim light, it dilates (becomes larger) to allow more light to enter.
• 
  Optical nerve:
  This nerve transmits visual information from the retina to the brain. It is involved in vision but does not control the amount of light entering the eye.
• 
  Retina:
  This is the light-sensitive layer at the back of the eye that contains photoreceptor cells (rods and cones) which detect light. It is where the image is formed, but it does not regulate the amount of incoming light.
• 
  Ciliary muscles:
  These muscles are responsible for changing the shape of the lens to focus on objects at different distances (accommodation). They do not directly control the amount of light entering the eye.

Step 2: Identify the part of the eye responsible for regulating light entry.
The pupil, by changing its size, controls the amount of light that enters the eye. The iris, which surrounds the pupil, is the muscular diaphragm that regulates the pupil's size based on the intensity of light.