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How do optical fibres utilise total internal reflection?

Optical fibres utilise total internal reflection by bouncing light signals down the fibre to transmit data.

Optical fibres are thin strands of glass or plastic that are used to transmit data in the form of light signals. The principle of total internal reflection is fundamental to their operation. This is a phenomenon that occurs when a wave, such as light, hits a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface.

In the case of optical fibres, the fibre core, through which the light travels, is surrounded by a cladding with a lower refractive index. When light signals enter the fibre, they do so at an angle that ensures they hit the boundary between the core and the cladding at an angle greater than the critical angle. This means that all the light is reflected back into the core, rather than refracting into the cladding. This reflection happens repeatedly, causing the light to zig-zag or 'bounce' down the fibre.

This bouncing of light, or total internal reflection, allows the light signals to travel long distances with very little loss of signal strength. It also means that the signals can be transmitted around bends and corners in the fibre, as the light will always be reflected back into the core, regardless of the angle at which it hits the boundary.

The use of total internal reflection in optical fibres allows for high-speed, high-capacity data transmission. It is a key technology in telecommunications, enabling the fast, reliable internet connections that we rely on today.

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