Question

A beam of monochromatic blue light of wavelength $4200\, ?? in air travels in water of refractive index$4/3$. Its wavelength in water will be:

• A. $4200, ??
• B. $5800, ??
• C. $4150 ,??
• D. $3150, ??

Answer 1

Answer: (D)

$3150, ??

Answer 2

Wavelengh $\lambda \propto \frac{1}{\mu}$
$\therefore \frac{\lambda_{2}}{\lambda_{1}}=\frac{\mu_{1}}{\mu_{2}}=\frac{3}{4} \,\,\left(\because 1 \mu_{2}=\frac{4}{3}\right)$
or $\lambda_{2}=\frac{3}{4} \lambda_{1}=\frac{3}{4} \times 4200=3150, ??