Total internal reflection

How it is used

Abbreviated TIR. It only happens when light travels from a higher to a lower refractive index. For a boundary with air, the critical angle C satisfies sin C = 1/n. Used in optical fibres, endoscopes, prism binoculars and the sparkle of diamonds.

Example sentences

1. Optical fibres carry light over long distances by total internal reflection.

2. Increase the angle until the ray no longer leaves the block: that is total internal reflection.

Common collocations

• critical angle
• optical fibre
• refractive index
• undergo total internal reflection

Related terms

• reflectionThe bouncing back of light, sound or another wave when it hits a surface. For a flat mirror, the angle of reflection equals the angle of incidence.
• refractionThe change in direction of a wave as it passes from one material into another, caused by a change in its speed. It is why a straw looks bent in a glass of water.
• lensA curved piece of glass or plastic that bends light by refraction to form an image. A converging lens brings light rays together; a diverging lens spreads them out.
• electromagnetic spectrumThe full range of electromagnetic waves, ordered by wavelength or frequency: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.

More terms: Light and Optics

• focal length