In opticle fibres,the refractive index of the core is

Options

A. greater than that of the cladding
B. equal to that of the cladding
C. smaller than that of the cladding
D. independent of that of the cladding

Explanation

To solve the question regarding the refractive index of the core in optical fibers, we need to understand the basic structure and functioning of optical fibers.

### Step-by-Step Solution:

1. **Understanding Optical Fiber Structure**:
- An optical fiber consists of three main parts: the core, the cladding, and the protective jacket.
- The core is the innermost part where light travels, surrounded by the cladding, which has a lower refractive index than the core.

2. **Principle of Total Internal Reflection**:
- Optical fibers operate on the principle of total internal reflection.
- For total internal reflection to occur, the light must travel from a medium with a higher refractive index (the core) to a medium with a lower refractive index (the cladding).

3. **Refractive Index Comparison**:
- Since the core must have a higher refractive index than the cladding for total internal reflection to take place, we can conclude that:
\[ n_{core} > n_{cladding} \]
- This means that the refractive index of the core is greater than that of the cladding.

4. **Conclusion**:
- Therefore, the correct answer to the question is that the refractive index of the core is greater than that of the cladding.

### Final Answer:
The refractive index of the core in optical fibers is greater than that of the cladding.

---