Question

When the same monochromatic ray of light travels through glass slab and through water, the number of waves in glass slab of thickness 6 cm is same as in water column of height 7 cm. If refractive index of glass is `1.5`, then refractive index of water is
A. `1.258`
B. `1.269`
C. `1.286`
D. `1.310`

Answer 1

Correct Answer - C
No. of waves in the glass slab of thickness `t_g` = No. of waves in the water column of height `h_w`. The optical path in a medium of thickness t, and R.I. `mu` is `mu xx t` .
Using this we get ,
`mu_g xx t_g = mu_w xx h_w`
`:. ""mu_w=(mu_g xx t_g)/(h_w)=(1.5 xx 6)/(7)=(9)/(7)=1.286`