Question

A light wave of frequency $5\times {10}^{14}Hz$ passes through a medium of refractive index 2.4. Its wavelength in the medium will be:

• A. $1\times {10}^{-7}m$
• B. $4\times {10}^{-7}m$
• C. $3.3\times {10}^{-7}m$
• D. $2.5\times {10}^{-7}m$

Answer 1

Answer: (D)

$2.5\times {10}^{-7}m$

$\mu =\frac{{\lambda }_v}{{\lambda }_m}$

where, ${\lambda }_v$ is in vacuum and ${\lambda }_m$ is in medium.

${\lambda }_v=\frac{c}{f}$

${\lambda }_v$=$\frac{3\times {10}^8}{5\times {10}^{14}}$

${\lambda }_v=0.6\times {10}^{-6}$

$2.4=\frac{0.6\times {10}^{-6}}{{\lambda }_m}$

${\lambda }_m=2.5\times {10}^{-7}$ m