Question: The frequencyofalight wave in a material is $2 \times 10^{14} \mathrm{~Hz}$ and wavelength is $5000 \AA$. The refractive index of material will be
A) 1.50
B) 3.00
C) 1.33
D) 1.40
Answer: 3.00
Sol:
$\mu=\frac{\text { velocity of light in vacuum }(c)}{\text { velocity of light in medium }(v)}$ $$ \begin{aligned} & \therefore \quad v=v \lambda=2 \times 10^{14} \times 5000 \times 10^{-10}=10^8 \mathrm{~m} / \mathrm{s} \ & \therefore \quad \mu=\frac{c}{v_{\text {med }}}=\frac{3 \times 10^8}{10^8}=3 \end{aligned} $$
