## **Core Concept**
The refractive index is a measure of how much a light beam bends as it passes from one medium to another. In the context of the eye, different parts have different refractive indices, which contribute to the eye's overall ability to focus light. The cornea, being the outermost layer of the eye, plays a significant role in this process.

## **Why the Correct Answer is Right**
The cornea has a refractive index of approximately 1.376. This value is crucial for understanding how light is initially bent as it enters the eye. The refractive indices of the various parts of the eye are as follows: cornea (1.376), aqueous humor (1.336), lens (1.406), and vitreous humor (1.336). The cornea contributes significantly to the eye's total optical power, primarily because of the large difference in refractive index between air (approximately 1.00) and the cornea.

## **Why Each Wrong Option is Incorrect**
- **Option A:** 1.2 - This is too low for the refractive index of the cornea. Refractive indices of biological tissues are usually close to that of water (1.33) but can vary based on their composition.
- **Option B:** 1.5 - This is higher than the actual refractive index of the cornea. While the lens has a higher refractive index (around 1.406), the cornea's index is lower than this value.
- **Option D:** 2.0 - This is significantly higher than the refractive index of any part of the eye, including the cornea. Such high refractive indices are more characteristic of dense materials like glass or certain plastics.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the cornea contributes about 2/3 of the eye's total refractive power, mainly due to the air-cornea interface. This is why corneal injuries or diseases can significantly affect vision, and why refractive surgeries like LASIK are effective for correcting vision by altering the cornea's shape.

## **Correct Answer:** C. 1.376.