A ray of light travelling in a transparent medium of refractive index `mu` falls, on a surface separating the medium from air at an angle of incidence of `45^(@).` for which of the following value of `mu` the ray can undergo total internal reflection ?

Options

A. `mu = 1.33`
B. `mu =1.40`
C. `mu = 1.50`
D. `mu = 1.25`

Answer

C

Explanation

For total internal reflection
`sin i gt sin C`
where
`i=` angle of incidence
`C=` critical angle
But, `sin C = (1)/(mu)`
`:. sin u gt (1)/(mu)` or `mu gt (1)/(sin i)`
`mu gt (1)/(sin 45^(@)) (I = 45^(@)` (Given)
`mu gt sqrt(2)`
Hence, option (C) is correct.