The refractive index of the material of a prism of refracting angle `45^@` is `1.6` for a certain monochromatic ray. What will be the minimum angle of incidence of this ray on the prism so that no TIR takes place as the ray comes out of the prism.

Explanation

`theta_(C) = sin^(-1)((1)/(mu)) = sin^(-1)((1)/(1.6)) = 38.7^(@)`
`r_(2) = theta_(C) = 38.7^(@)`
`:. r_(1) = A - r_(2) = 45^(@) - 38.7^(@) = 6.3^(@)`
Now applying, `mu = (si8ni_(1))/(sinr_(2))`
we can find `i_(1)`.