Two beams of light are incident normally on water (R.l. = `4/3`). If the beam 1 passes through a glass (R.l. = `3/2`) slab of height h as shown in the figure, the time difference for both beams for reaching the bottom is

Options

A. Zero
B. `h/6C`
C. `6h/C`
D. `h/6C`

Answer

D

Explanation

The refractive index of glass is greater than that of water. Therefore the speed of light in glass is less.than that of water. It is given as
`v=C/n`,where C=`3xx10^(8)m//s`
v=speed of light in a medium of R.I.n
:.The time difference for the rays
`Deltat=t_(1)-t_(2)=h/v_(g)-h/v_(w)=h/(C//n_(g))-h/(C_(w)//n_(w))=h/C n_(g)-n_(w)`
`impliesDeltat=h/C[3/2-4/3]=h/6C`
Hence(D) is correct.