Which of the following is used in optical fibres?

Options

A. Endoscopy
B. High speed internet traffic
C. Radio, TV & Telephone signals
D. All of these

Answer

### Step-by-Step Solution:

1. **Understanding Optical Fibers**: Optical fibers are thin strands of glass or plastic that transmit light signals over long distances. They consist of a core and a cladding layer.

2. **Core and Cladding**: The core of the optical fiber has a higher refractive index (μ1) compared to the cladding (μ2). This difference in refractive indices is crucial for the functioning of optical fibers.

3. **Total Internal Reflection**: For light to be transmitted efficiently through the optical fiber, it must undergo total internal reflection. This occurs when light travels from a denser medium (core) to a rarer medium (cladding) at an angle greater than the critical angle.

4. **Applications of Optical Fibers**:
- **Endoscopy**: Optical fibers are used in medical instruments like endoscopes, which allow doctors to view the inside of the body by transmitting light and images from internal surfaces.
- **High-Speed Internet**: Fiber optic cables are used for internet connections, transmitting large amounts of data at high speeds compared to traditional copper wires.
- **Telecommunication**: They are also used in radio, television, and telephone signals, providing efficient transmission over long distances.

5. **Conclusion**: Given the applications and the principle of total internal reflection, we can conclude that optical fibers are used in various fields, including medicine and telecommunications.

### Final Answer:
All of the mentioned applications (endoscopy, high-speed internet, and telecommunication) utilize optical fibers. Therefore, the correct answer is option number four.

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