Question

Consider the following statements in the context of human eye:
(a) The diameter of the eye ball is about 2.3 cm.
(b) Iris is a dark muscular diaphragm that controls the size of the pupil.
(c) Most of the refraction for the light rays entering the eye occurs at the crystalline lens.
(d) While focusing on the objects at different distances the distance between the crystalline lens and the retina is adjusted by ciliary muscles.
The correct statements are –

• A. (a) and (b)
• B. (a), (b) and (c)
• C. (b), (c) and (d)
• D. (a), (c) and (d)

Answer 1

The Correct Option is A

Step 1: Analyzing statement (a):
The diameter of the eyeball is about 2.3 cm. This statement is correct. The average diameter of the human eyeball is approximately 2.3 cm, which is consistent with the dimensions of a typical human eye.

Step 2: Analyzing statement (b):
Iris is a dark muscular diaphragm that controls the size of the pupil. This statement is also correct. The iris is a circular structure that surrounds the pupil and is responsible for regulating the amount of light entering the eye by controlling the size of the pupil. It adjusts the pupil size based on light intensity.

Step 3: Analyzing statement (c):
Most of the refraction for the light rays entering the eye occurs at the crystalline lens. This statement is incorrect. While the crystalline lens plays a role in focusing light on the retina, most of the refraction occurs at the cornea, not the crystalline lens. The cornea provides the majority of the focusing power of the eye.

Step 4: Analyzing statement (d):
While focusing on objects at different distances, the distance between the crystalline lens and the retina is adjusted by ciliary muscles. This statement is also incorrect. The ciliary muscles do not change the distance between the lens and the retina. Instead, they alter the shape of the crystalline lens (a process called accommodation), which helps focus light from objects at different distances onto the retina.

Step 5: Conclusion:
The correct statements are (a) and (b). These are the only accurate statements regarding the human eye.

Correct Answer: (a) and (b)