Question

Light of frequency $5 \times 10^{14}\,Hz$ is travelling in a medium of refractive index $1.5$. What is its wavelength? $\left(C=3 \times 10^{8} \,m / s \right)$

• A. $ 4000\,\mathring{A}$
• B. $ 4500\,\mathring{A}$
• C. $ 6000\,\mathring{A}$
• D. $ 9000\,\mathring{A}$

Answer 1

Answer: (A)

Refractive index, $\mu=\frac{\lambda}{\lambda_{m}}$
or $\lambda_{m}=\frac{\lambda}{\mu}$
Putting $\lambda=\frac{c}{v}$
Than $\lambda_{m}=\frac{c}{v \mu}$
So, $\lambda_{m}=\frac{3 \times 10^{8}}{5 \times 10^{14} \times 1.5} m$
$=4000\,\mathring{A}$