A light ray falling at an angle of` 45^@` with the surface of a clean slab of ice of thickness 1.00 m is refracted into it at an angle of 30°. Calculate the time taken by the light rays to cross the slab. Speed of light in vacuum `= 3 xx 10^8ms^-1`

Answer

D

Explanation

We know `(sini)/(sinr)=(3xx10^8)/v`
`=(sin45^@)/(sin30^@)=((1/sqrt2))/((1/2))`
=2/sqrt2=sqrt2`
`rarr v=(3xx10^8)/sqrt2m/sec`
`Distance traveled by light in the slab is
`=x=(1m)/(cos30^@)=2/sqrt3m`
`So, time taken `=2/sqrtxxsqrt2/(3xx10^8)`
`=0.54xx10^-8`
`=5.4xx10^-9sec`