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Question
Answer the following question.
Define the critical angle of incidence and obtain an expression for it.
Solution
- The critical angle for a pair of refracting media can be defined as that angle of incidence in the denser medium for which the angle of refraction in the rarer medium is 90°.
- Let n be the relative refractive index of a denser medium with respect to the rarer.
- Then, according to Snell’s law,
n = `"n"_"denser"/"n"_"rarer"=(sin"r")/(sin"i"_"c")=(sin90°)/(sin"i"_"c")`
∴ sin (ic) = `1/"n"`
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