A monochromatic light beam travels through a transparent medium. It covers a distance of 40 cm in 2 ns . If the wavelength of the light in this medium is 400 nm , the frequency of the light in vacuum is :

Step-by-step solution

Speed of light in the medium is given by v = distance time v = 40 10⁻² m 2 10⁻⁹ s = 2 10^8 m/s The frequency of the light in the medium is f = v _ medium f = 2 10^8 400 10⁻⁹ = 2 10^8 4 10⁻⁷ = 0.5 10¹⁵ Hz = 5.0 10¹⁴ Hz The frequency of light remains invariant when it travels from one medium to another. Therefore, the frequency of the light in vacuum is the same as its frequency in the medium, which is 5.0 10¹⁴ Hz . Answer: 5.0 10¹⁴ Hz