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Question
Explain the term critical angle with the aid of a labelled diagram.
Solution
The angle of incidence in the denser medium corresponding to which the angle of refraction in the rarer medium is 90° is called the critical angle.
A light beam bends away from normal when it moves from a denser medium (water) to a rarer medium (air).
∠r ∠i as shown by AB, BD.
Hence, as we raise the angle of incidence, ∠r rises in tandem with AE. A stage is reached when the angle of refraction becomes 90°, or parallel to the separation surface, as the angle of incidence increases. Then ∠i is referred to as the crucial angle.
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RELATED QUESTIONS
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State the approximate value of the critical angle for glass-air surface.
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Critical angle is the angle of ______ in denser medium for which the angle of ______ in rarer medium is ______.
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Copy the diagram given below and complete the path of the light ray PQ, as it emerges out of the prism by necessary angles. The critical angle of glass is 42°:
