Q.Light takes t1 sec to travel a distance x cm in vacuum and takes t2 sec to travel 10x cm in a medium. The critical angle corresponding to the media is

(a)sin^{-1}(10t_{1}/t_{2})

(b) sin^{-1}(t_{2}/(10t_{1} ))

(c) sin^{-1}(10t_{2}/t1 )

(d) sin^{-1}(t_{1}/(10t_{2} ))

Ans:(a)

Sol: t_{1} = x/c , t_{2} = 10x/(c/μ ) = 10xμ/c

Hence , t_{2} = 10μt_{1} => μ= t_{2}/10t_{1}

sinθ = 1/μ =10t_{1}/t_{2}

θ = sin^{−1}(10t_{1}/t_{2})