Question

The wavelength and frequency of beam of light in water of refractive index 4/3 having wavelength 0.48 micron in air are

• A. $0.16\times {10}^{-6}m,6.25\times {10}^{14}Hz$
• B. $0.36\times {10}^{-6}m,6.25\times {10}^{14}Hz$
• C. $0.36\times {10}^{-6}m,3.25\times {10}^{14}Hz$
• D. $0.26\times {10}^{-6}m,6.25\times {10}^{14}Hz$

Answer 1

The correct option is B $0.36\times {10}^{-6}m,6.25\times {10}^{14}Hz$

Wavelength of light in air ${\lambda }_a=0.48\times {10}^{-6}m$

Wavelength of light in water ${\lambda }_m=\frac{{\lambda }_a}{\mu }=\frac{0.48\times {10}^{-6}}{4/3}=0.36\times {10}^{-6}m$
Frequency of light in air
$\nu =\frac{c}{{\lambda }_a}=\frac{3\times {10}^8}{0.48\times {10}^{-6}}=6.25\times {10}^{14}Hz$
On passing through water (medium), frequency does not change. Hence, it will be $6.25\times {10}^{14}Hz$ in water as well.