How does light travel through an optical fibre? - Leaving Cert Physics - Question e - 2013

Light travels through an optical fibre primarily through a process known as total internal reflection. This phenomenon occurs when light travels from a medium with a higher refractive index, such as glass, to a medium with a lower refractive index, such as air, at an angle greater than the critical angle.

1. Propagation of Light: When light is emitted into the fibre from a source, it enters the core of the optical fibre. The core has a high refractive index, and the surrounding cladding has a lower refractive index.

2. Total Internal Reflection: As the light hits the boundary between the core and cladding, if the angle of incidence exceeds the critical angle, the light is reflected back into the core rather than refracting into the cladding. This is total internal reflection.

3. Continuous Reflection: This process is repeated along the length of the fibre, allowing the light to travel significant distances with minimal loss of intensity.

4. Diagram Representation: A diagram illustrating light rays within an optical fibre would show the incident light striking the core-cladding boundary at an angle greater than the critical angle and being reflected within the core.

Overall, optical fibres utilize this properties effectively to transmit signals over long distances with high fidelity.