Question

The index of refraction of fused quartz is 1.472 for light of wavelength 400 nm and is 1.452 for light of wavelength 760 nm .Find speeds of light of these wavelength in fused quartz ?

Answer 1

The refractive index for air is $\mu =1$

and speed of lght in air is $v=3\times {10}^{8}m/s$

We know that, the speed of the light in a medium of refractive index $\mu$ is gelated as:

$\frac{{\mu }_1}{{\mu }_2}=\frac{v_1}{v_2}$

So, $\frac{1.472}{1}=\frac{3\times {10}^8}{v_{400}}$

$\Rightarrow v_{400}=2.04\times {10}^{8}m/sec$.

Aagain, for the light of wavelength $760nm$:

$\frac{1452}{1}=\frac{3\times {10}^8}{v_{760}}$

$\Rightarrow v_{760}=2.07\times {10}^{8}m/\sec$