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    Question

    A periscope works on the principle of

    A refraction Correct Answer Incorrect Answer
    B total internal reflection Correct Answer Incorrect Answer
    C diffraction Correct Answer Incorrect Answer
    D reflection Correct Answer Incorrect Answer

    Solution

    Total internal reflection (TIR) is the phenomenon that involves the reflection of the entire incident light off the boundary. Glass prisms can be shaped to produce total internal reflection and as such are employed in binoculars, periscopes, telescopes, and other optical instruments. For the prism used in periscope, the light rays hit the inside surface at an angle greater than the critical angle of 42 and hence they are internally reflected.

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