Which is true for optical fibers?

Options

A. Core has higher refractive index than cladding
B. Core has less refractive index than cladding
C. Both have same refractive index
D. None of these

Explanation

### Step-by-Step Text Solution:

1. **Understanding Optical Fibers**: Optical fibers are thin strands of glass or plastic that transmit light signals over long distances. They are primarily used in telecommunications and medical instruments.

2. **Principle of Operation**: Optical fibers operate on the principle of Total Internal Reflection (TIR). This phenomenon occurs when light travels from a denser medium to a rarer medium at an angle greater than the critical angle, resulting in the light being completely reflected back into the denser medium.

3. **Structure of Optical Fibers**: An optical fiber consists of two main components:
- **Core**: The central part of the fiber, which is made of a material with a higher refractive index (denser medium). This is where the light travels.
- **Cladding**: The outer layer surrounding the core, made of a material with a lower refractive index (rarer medium). This layer helps to keep the light within the core through TIR.

4. **Refractive Index**: For Total Internal Reflection to occur, the refractive index of the core must be greater than that of the cladding. This ensures that when light travels from the core to the cladding, it reflects back into the core instead of passing through.

5. **Conclusion**: Therefore, the statement that is true for optical fibers is that they utilize the principle of Total Internal Reflection, where the core has a higher refractive index than the cladding.