A beam of light has a wavelength of 506 nanometers. What is the frequency of the light? What colour is the light?

For electromagnetic waves;

speed = wavelength x frequency

3x10^8 = 506x10^-9 x f = > f = 5.92885375 x 10^14

To determine the colour, you need to check the visible light spectrum. Between wavelengths 495 to 570, the light is green.

This is a physics question though.