How does the intensity of scattered light depend on the wavelength of incident light? State the condition when this dependence hold.

The scattering of light is not same for all wavelengths of incident light.

The intensity of scattered light is found to be inversely proportional to the fourth power of the wavelength of light

( i.e., I ∝ $\dfrac{1}{λ^4}$ ).

The above relation holds true, when the air molecules are smaller in size than the wavelength of incident light.

The air molecules of size bigger than the wavelength of incident light, scatter the light of all wavelengths of white light to the same extent.

For example — The wavelength of violet is least (λ = 4000 Å) and that of red light is most (λ = 8000 Å), therefore, from the incident white light, violet light is scattered most and the red light is scattered the least. (violet light is scattered nearly 16 times more than the red light).