Science glossary film: Total internal reflection

The complete reflection of a light ray within a transparent material. Total internal reflection occurs when the angle of incidence – that is, the angle at which the light ray meets the surface of the material – is higher than what’s called the critical angle. For glass, the critical angle is around 42 degrees. Once the angle of the ray exceeds this, the light stops refracting out of the material and is instead completely reflected. Fibre optic cables use total internal reflection to transmit information in the form of light. Because the light is totally internally reflected, it stays within the cable, preventing loss of information, even over long distances.

Total internal reflection occurs when the angle of incidence – that is, the angle at which the light ray meets the surface of the material – is higher than what’s called the critical angle. For glass, the critical angle is around 42 degrees. Once the angle of the ray exceeds this, the light stops refracting out of the material and is instead completely reflected. Fibre optic cables use total internal reflection to transmit information in the form of light. Because the light is totally internally reflected, it stays within the cable, preventing loss of information, even over long distances.