The speed of light in medium A is `2.0xx10^8m//sec` and that in medium B is `2.4xx10^8m//sec`. The critical angle of incidence for light tending to go from medium A to medium B is

Options

A. `sin^(-1) ((5)/(6))`
B. `sin^(-1)((5)/(12))`
C. `sin^(-1)((2)/(3))`
D. `sin^(-1) ((3)/(4))`

Answer

A

Explanation

`(V_(A))/(V_(B)) = ( 2 xx 10^(8))/(2.4 xx 10^(8)) = (5)/(6) = ""_(A) n_(B)`
= R.I. of medium B w.r.t. medium A
`therefore v_(A) gt v_(B)`
B is the rarer medium and A is the denser medium
`therefore ` For light travelling from A to B , we can get critical angle (C) and sin C = R.I. of the rarer medium w.r.t the denser medium = `""_(A) n_(B)`
`therefore` sin C = `(5)/(6) therefore C = sin^(-1) ((5)/(6))`