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, ${\lambda }_m=\frac{3\times 10^8}{5\times 10^{14}\times 1.5}m$
$=4000\mathring{A}$