A ray of light passing through the medium of refractive index `mu_(1)` is incident on the surface of separation of another medium of refractive index `mu_(2)` . A part of the ray is reflected and another part is refracted. What should be the angle of incident so that reflected ray and the refracted ray are at right angles to each other?

Explanation

According to Fig. 2.277,
`i + 90^(@) + r = 180^(@)`
`or, " " r = 90^(@) - i`
By Snell.s law,
`mu_(1) sini = mu_(2) sinr`
`therefore " " (sini)/(sin(90^(@) - i)) = (mu_(2))/(mu_(1)) or, (sini)/(sinr) = (mu_(2))/(mu_(1))`
`or " " tani = (mu_(2))/(mu_(1)) oritan^(-1) ((mu_(2))/(mu_(1)))`