Chapter 24 - Physical Optics: The Wave of Nature of Light - Learning Path Questions and Exercises - Multiple Choice Questions - Page 839: 15

(c) red

For particles such as air molecules, which are much smaller than the wavelength of light, the intensity of the scattered light is inversely propotional to the wavelength to the fourth power $\frac{1}{V^{4}}$. This relationship between wavelength and scattering intensity is called Rayleigh scattering. Since red light have greatest wavelength it is scattered least.