Q: The refractive index of glass with respect to water is 9/8. If the velocity and wavelength of light in glass are 2 × 10^{8} m/s and 4000 A° respectively, find the velocity and wavelength of light in water.

Sol: $\large ^w\mu_g = \frac{\mu_g}{\mu_w} = \frac{v_w}{v_g} $

$\large \frac{9}{8} = \frac{v_w}{2 \times 10^8 } $

v_{w} = 2.25 × 10^{8} m/s

$\large \frac{\mu_g}{\mu_w} = \frac{\lambda_w}{\lambda_g} $

$\large \frac{9}{8} = \frac{\lambda_w}{4000} $

λ_{w} = 4500 A°