Question

Monochromatic light is refracted from air into a medium of refractive index n. The ratio of the wavelengths of the incident and the refracted waves is ______.

Options

• 1 : 1

• 1 : n

• n : 1

• n² : 1

Answer 1

Monochromatic light is refracted from air into a medium of refractive index n. The ratio of the wavelengths of the incident and the refracted waves is n : 1.

Explanation:

When monochromatic light goes from air into a medium with a refractive index (n), its frequency remains the same but its speed decreases by a factor of (n). Since wavelength is proportional to speed, the wavelength in the medium is shorter by a factor (n). Thus, the ratio of the wavelengths of the incident wave (in air) to the refracted wave (in medium) is `(lambda_"air"/lambda_"medium" = n : 1)`.