If the critical angle for total internal reflection, from a medium to vacuum is `30^(@)`, then velocity of light in the medium is

Options

A. `6 xx 10^(8) m//sec`
B. `3 xx 10^(8) m//sec`
C. `2 xx 10^(8) m//sec`
D. `1.5 xx 10^(8) m//sec`

Answer

D

Explanation

`c = 30^(@), v_(m) = ?`
`._(m)mu_(a) = sin c = (v_(m))/(v_(a))`
`:. v_(m) = v_(a) xx sin c`
`= 3 xx 10^(8) xx sin 30`
`= 1.5 xx 10^(8) m//s`