The difference in speeds of a rya of light in galss and wate is ` 2.5 xx 10^(7) m//s `. If the R.I. of glass and water are `(3)/2 and (4)/3` respectively, then the velocity of light in air is

Options

A. a) `2 xx 10^(8) m//s `
B. b) `2.25 xx 10^(8) m//s `
C. c) `3 xx 10^(8) m//s `
D. d) `2.5 xx 10^(8) m//s `

Answer

C

Explanation

`V_g=(V_(a))/(3//2)=(2)/(3)V_a, V_w=V_w=(V_a)/(4//3)=(3)/(4) V_a `
`:. (3)/(4)V_a -(2)/(3)V_a=(1)/(12)V_a=2.5 xx 10^(7)`
`:. V_a=12 xx 2.5 xx 10^(7) =3 xx 10^(8) m//s `