Question

The wavelength of light in a medium is $\lambda ={\lambda }_0/\mu$, where $\lambda$ is the wavelength in vacuum. A beam of red light $\left({\lambda }_0=720\mathrm{nm}\right)$ enters water. The wavelength in water is $\lambda ={\lambda }_0/\mu =540\mathrm{nm}$. To a person under water, does this light appear green?

Answer 1

Colour of light will depend only on the frequency of light and not on the wavelength of the light. So, light will appear red to an observer under water.