In an optical fibre, the light signal is transmitted by

Options

A. Refraction at the core-cladding interface
B. Interference between the incident and inflected waves
C. Repeated total internal reflections at the core and cladding interface
D. Polarisation of optical signals.

Answer

**Step-by-Step Solution:**

1. **Understanding Optical Fibres**: Optical fibres are thin strands of glass or plastic that transmit light signals over long distances. They are used in communication systems to carry data in the form of light pulses.

2. **Principle of Light Transmission**: The light signal in an optical fibre is transmitted through the principle of total internal reflection. This occurs when light travels from a medium with a higher refractive index (the core of the fibre) to a medium with a lower refractive index (the cladding).

3. **Total Internal Reflection**: For total internal reflection to occur, the angle of incidence must be greater than the critical angle specific to the materials used in the fibre. This allows the light to be contained within the core of the fibre and travel along its length without escaping.

4. **Modes of Propagation**: There are two modes of light propagation in optical fibres:
- **Single-mode fibre**: This allows only one mode of light to propagate, which is used for long-distance communication.
- **Multi-mode fibre**: This allows multiple modes of light to propagate, which is generally used for shorter distances.

5. **Applications**: Optical fibres are widely used in telecommunications, internet connections, and medical instruments due to their high bandwidth and low signal loss.

**Final Answer**: In an optical fibre, the light signal is transmitted by total internal reflection.

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