![]() If the angle of incidence is increased further, so that it is greater than the critical angle, the light will be totally internally reflected. Optical fibres are also unaffected by electromagnetic interference. For larger incidence angles, there is no total internal reflection, and much of the incident light will not be reflected at the corecladding boundary. Metal wires are preferred for transmission in optical fibre communication as signals travel with fewer damages. The diagram below shows light hitting the glass-air boundary at an angle that is equal to the critical angle. Optical fibre is the technology associated with data transmission using light pulses travelling along with a long fibre which is usually made of plastic or glass. This difference in the indices causes total internal reflection to occur at the core-cladding boundary along the length of the fiber. You will be reminded of this fact in the exam. The critical angle varies for different materials, but it is useful to know that it is around 42 degrees for glass. This angle of incidence is called the critical angle. ![]() At a certain angle of incidence, the light will refract 90 degrees and travel along the boundary between the two media. The conditions required for total internal reflection (TIR) to occur are: the light must be travelling from a more dense medium into a less dense medium (ie glass to air) the angle of incidence. ![]() The diagram below shows the light refracting from glass into air.Īs the angle of incidence is increased, the angle of refraction also increases. The angle of refraction is greater than the angle of incidence. ![]() When light travels from a denser medium, eg glass, to a less dense medium, eg air, the speed of the light increases and the light refracts away from the normal. When light travels into a different medium, the speed of the light changes and the light is refracted (see The features of waves ). Optical fibers are used to study internal organs in the process called endoscopy they transmit light basing on the phenomenon called total internal reflection. The conditions for total internal reflection ![]()
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