Question

Essential conditions for total internal reflection.​

Answer 1

There are two necessary conditions for total internal reflection :

• The light must travel from a denser to a rarer medium.

• The angle of incidence must be greater than the critical angle for the pair of media.

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☆ Note :

• In the process of total internal reflection, 100% energy (or intensity) of light is reflected back. No other device such as plane mirror, etc. produces 100% reflection (due to absorption and refraction of some part of light). Due to this property, the phenomenon of total internal reflection is used in the construction of periscope, binocular and certain types of camera in which a total reflecting prism replaces a plane mirror for reflection of light.

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Answer 2

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For total internal reflection to take place (i) light must travel from a denser medium to a rarer medium and (ii) the angle of incidence inside the denser medium must be greater than the critical angle.

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