As shown in Fig. `PQ` is a ray incident on prism `ABC`. Show the corresponding refracted and emergent rays. The critical angle for the material of the prism is `45^@`. What is refractive index of the material of prism ?
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Answer

`sqrt(2)`

Explanation

As `PQ` is normal to `AB`,
`:. i_1 = 0, r_1 = 0`
The ray goes straight along `PQR. At R, sqrt(i) = 45^@` which is critical angle of material of the prism.
Therefore, `QR` suffers total internal reflection at `R` and goes along `RS`
`mu = (1)/(sin C) = (1)/(sin 45^@) = (1)/(1//sqrt(2)) = sqrt(2)`.