Question

Consider the following statements in the context of human eye:

1. The diameter of the eye ball is about 2.3 cm.
2. Iris is a dark muscular diaphragm that controls the size of the pupil.
3. Most of the refraction for the light rays entering the eye occurs at the crystalline lens.
4. 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:

Options

• a and b

• a, b and c

• b, c and d

• a, c and d

Answer 1

a and b

Explanation:

Adult eyeballs measure around 2.3 cm in diameter. The iris is the dark muscular diaphragm, whereas the ciliary muscle adjusts the focal length to focus images on the retina. The eye's initial surface, where light transitions from air to the cornea, has the most substantial shift in its index of refraction. The cornea accounts for around 80% of refraction, whereas the inner crystalline lens accounts for 20%.