The wave number (li) of a radiation with X, = 2 x 10^8 nm will be,

Explanation

Option Ais correct.The wave number (ν) of a radiation with wavelength λ = 2 x 10^8 nm will be 0.5 x 10^-8 nm^-1. The wave number is defined as the reciprocal of the wavelength. In other words, it is the number of waves per unit distance. The unit for wave number is usually expressed in cm^-1, but it can also be expressed in nm^-1. The wavelength of a wave is the distance between two consecutive peaks or troughs of the wave. In the case of electromagnetic radiation, the wavelength is the distance between two consecutive crests of the wave. The wave number of a radiation can be calculated using the following formula: ν = 1/λ where: ν is the wave number λ is the wavelength In this case, the wavelength is given as 2 x 10^8 nm. So, the wave number can be calculated as follows: ν = 1/λ = 1/(2 x 10^8 nm) = 0.5 x 10^-8 nm^-1 Therefore, the wave number of a radiation with wavelength λ = 2 x 10^8 nm will be 0.5 x 10^-8 nm^-1.