Question

The amount of light entering the human eye is controlled by:

• A. Ciliary muscles
• B. Pupil
• C. Cornea
• D. Iris

Hint:

The iris controls the size of the pupil, which regulates the amount of light entering the eye, ensuring proper vision.

Answer 1

The Correct Option is D

Step 1: Understanding the function of the iris in the human eye.
- The iris is the colored part of the eye that surrounds the pupil.
- It contains muscles that contract or relax to adjust the size of the pupil.
- The pupil regulates the amount of light entering the eye.

Step 2: Why the iris controls light entry.
- In bright light, the iris constricts, making the pupil smaller to limit the amount of light entering.
- In dim light, the iris expands, making the pupil larger to allow more light in.
- This automatic adjustment helps protect the retina from excessive light and ensures clear vision.
Step 3: Analyzing the options.
- Ciliary muscles (Option A): Control the shape of the lens for focusing, not light entry.
- Pupil (Option B): It is the opening through which light enters, but the iris controls its size.
- Cornea (Option C): It helps focus light onto the retina but does not control the amount of light entering.
- Iris (Option D): It adjusts the pupil size to control light entry.
Conclusion: Since the iris controls the amount of light entering the eye, the correct answer is (D) iris.