**Question:** Refractive index of the cornea is –

A.
B.
C.
D.

**Core Concept:** The refractive index is a measure of the ability of a substance to refract (bend) light. In the context of the cornea, it determines how light is bent upon entering the cornea, which plays a crucial role in focusing light on the retina for clear vision.

**Why the Correct Answer is Right:** The refractive index (n) is defined as the ratio of the speed of light in vacuum (c) to the speed of light in the medium (v):

n = c/v

In this case, the refractive index of the cornea is approximately 1.38, which is close to that of water (1.33). This indicates that the cornea has a similar refractive property to water, allowing light to bend efficiently as it passes from the air (vacuum) to the cornea and further into the eye.

**Why Each Wrong Option is Incorrect:**

**Option A:** This is incorrect because the refractive index of the cornea (1.38) is different from the number provided. A lower value indicates less efficient light bending, which would lead to poor vision.

**Option B:** This is incorrect as it is not related to the refractive index of the cornea, but rather describes the cornea's thickness. The cornea's thickness is important for its structure but not relevant to its refractive index.

**Option C:** This is incorrect because it describes the refractive index of a different substance, which is irrelevant to the cornea's refractive index.

**Option D:** This is incorrect because it is not related to the refractive index of the cornea but rather describes the refractive index of the vitreous humor (the gel-like substance within the eye). The refractive index of the vitreous humor is approximately 1.37, similar to that of the cornea (1.38).

**Core Concept (Clinical Pearls):**

Understanding the refractive index of the cornea is essential for understanding light refraction within the eye and the subsequent focusing process on the retina. The cornea's high refractive index helps to bend (refract) light efficiently as it enters the eye, allowing for clear vision. Any deviation from the correct refractive index can lead to visual impairment or distorted vision.