Question

A glass prism has a refracting angle of `60^@`. The angle of minimum deviation is `40^@`. If velocity of light in vacuum is `3 xx 10^8 m//s`. Calculate the velocity of light in glass. What is the angle of incidence ?

Answer 1

Correct Answer - `1.958 xx 10^8 m//s, 50^@`
Here, `A = 60^@, delta_m = 40^@, c = 3 xx 10^8 m//s, v = ?`
`i = ?`
`mu = (sin(A + delta_m)//2)/(sin A//2) = (sin(60^@ + 40^@)//2)/(sin 60^@//2) = (sin 50^@)/(sin 30^@)`
=`(0.7660)/(1//2) = 1.532`
As `mu = (c)/(v), v = (c)/(mu) = (3 xx 10^8)/(1.532) = 1.958 xx 10^8 m//s`
Also, `i = (A + delta_m)/(2) = (60^@ + 40^@)/(2) = 50^@`.