The refractive index of glass is 1.5. What is the speed of light in glass?

cbse
waveoptics

#1

(i) The refractive index of glass is 1.5. What is
the speed of light in glass? (Speed of light in vacuum is 3 x ${{10}^{8}}$ ${{ms}^{-1}}$)
(ii) Is the speed of light in glass independent of the colour of light? If not, which of the two colours red and violet travels slower in a glass prism?


#2

(i) Here, refractive index µ = 1.5
v=? c = 3 x ${{10}^{8}}$ ${{ms}^{-1}}$

As, µ = c/v ====> v = c/µ = 3 x ${{10}^{8}}$/1.5
= 2 x ${{10}^{8}}$ ${{ms}^{-1}}$

(ii) No, the refractive index and the speed of light in a
medium depend on wavelength, i.e. colour of light.
We know that, ${ µ }{ v}$ >
${ µ }
{ r}$. Hence, violet component of white light travels slower than the red component.