Refractive index of nucleus and Cortex are Respectively
**Core Concept**
The refractive index of the lens in the eye is a critical factor in determining its optical power. The lens is composed of a nucleus and a cortex, both of which have different refractive indices due to variations in water and protein content.
**Why the Correct Answer is Right**
The refractive index of the nucleus is higher than that of the cortex because the nucleus has a higher concentration of water and proteins, such as crystallins, which increase its refractive power. The cortex, on the other hand, has a lower concentration of these proteins and is more hydrated, resulting in a lower refractive index. This difference in refractive indices allows the lens to change shape and focus light on the retina during accommodation.
**Why Each Wrong Option is Incorrect**
* **Option A:** The refractive index of the nucleus is lower than that of the cortex, which is incorrect because the nucleus has a higher concentration of proteins and water, increasing its refractive power.
* **Option B:** The refractive indices of the nucleus and cortex are the same, which is incorrect because the differences in protein and water content between the two regions result in distinct refractive indices.
* **Option C:** The refractive index of the nucleus is not related to the refractive index of the cortex, which is incorrect because the two regions are closely related in terms of their refractive properties.
**Clinical Pearl / High-Yield Fact**
In age-related cataracts, the nucleus becomes more rigid and less optically clear due to the accumulation of water and proteins, leading to a decrease in its refractive index and a corresponding loss of lens power.
**Correct Answer:** A. 1.406 (nucleus) 1.386 (cortex)