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

`1.958 xx 10^(8)m//s, 50^(@)`

Explanation

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^(@)`