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

Options

A. 1.258
B. 1.269
C. 1.286
D. `1.310`

Answer

C

Explanation

As, we know number of waves in glass slab
`=` number of waves in water column
where, `mu_(g) =` refractive index in glass,
`mu_(w) =` refractive index of water column,
`h_(g) =` thickness of slab and `h_(w) =` height of water column.
Given, `mu_(g) = 15, h_(g) = 6 cm, h_(w) = 7` cm
`rArr mu_(w) = (mu_(g).h_(g))/(h_(w)) = (15 xx 6)/(7)`
`:. mu_(w) = 9/7 = 1.286`