Question

When monochromatic light is incident on a surface separating two media, the refracted and reflected light both have the same frequency as the incident frequency but the wavelength of refracted light is different. Explain why.

Answer 1

The frequency of light remains unchanged when it passes from one medium to another. This is because the energy of a photon is directly related to its frequency, and energy is conserved during the transition between media. However, the speed of light and the refractive index of the medium can change, which affects the wavelength of the light. The relationship between the speed of light \( c \), wavelength \( \lambda \), and frequency \( f \) is given by: \[ c = \lambda f \] Since the frequency \( f \) remains constant, any change in the speed of light \( c \) will result in a change in the wavelength \( \lambda \). This is why the wavelength of the refracted light changes as it moves from one medium to another.