Question

A ray of light of wavelength 4800 Angstrom suffers refraction from air to glass. Taking ${}_a{\mu }_g$​ = $\frac{3}{2}$, find the wavelength of light in glass.

• A. 1600
• B. 3200
• C. 6400
• D. 3600

Answer 1

The correct option is B

3200

${}_a{\mu }_g$ = $\frac{Velocityinvacuumorair}{Velocityinglass}$

$\frac{3}{2}$ = $\frac{f_{air}\times {\lambda }_{air}}{f_{water}\times {\lambda }_{water}}$​

But frequency of light remains unchanged in refraction. Thus, $f_{air}$​ = $f_{glass}$​

Now, $\frac{3}{2}$ = $\frac{{\lambda }_{air}}{{\lambda }_{glass}}$​

${\lambda }_{glass}$​ = wavelength in glass = $\frac{2}{3}$ ${\lambda }_{air}$​​

${\lambda }_{glass}$​ ​ = $\frac{2}{3}$ $\times$ 4800 = 3200 Angstrom.