Question

The frequency of a light wave in a material is $2 \times 10^{14} Hz$ and wavelength is $5000\, ?$. The refractive index of material will be

• A. 1.4
• B. 1.5
• C. 3
• D. 1.33

Answer 1

Answer: (C)

3

Answer 2

Velocity of light waves in material is
$v=v \lambda$ ...(i)
Refractive index of material is
$\mu=\frac{c}{v}$ ...(ii)
where $c$ is speed of light in vacuum or air
or $\mu=\frac{c}{v \lambda}$ ...(iii)
Given, $v=2 \times 10^{14} Hz$
$\lambda=5000 ?=5000 \times 10^{-10} m$
$c=3 \times 10^{8} m / s$
Hence, from E (iii), we get
$\mu=\frac{3 \times 10^{8}}{2 \times 10^{14} \times 5000 \times 10^{-10}}=3.00$