Scattering is a physical process by which a particle in the path of an electromagnetic wave continuously exstracts energy from the incident wave and reradiates that energy in all directions. In more detail, it occurs when a photon’s electromagnetic field hits a particle’s electric field in the atmosphere and is deflected into another direction. The Rayleigh scattering falls into the elastic scattering phenomena, in which the individual photon changes its direction of propagation but non its energy. The Rayleigh scattering involves air molecules (mainly N2 and O2) whose diameter (x) is much smaller (one-tenth at least) than the incident radiation wavelength (λ) (i.e., x << λ). The amount of scattered intensity (I) depends on the incident light wavelength (λ) and the refractive index (n) of air molecules. However, the refractive index can be considered relatively negligible as compared to the explicit wavelength term. In this way, the intensity scattered by air molecules in a specific direction is strongly dependent on the wavelength (λ), as expressed in the form Iλ~1/λ4. The inverse dependence of the scattered intensity on the wavelength to the fourth power allows at explaining the blue color of sky, caused by the scattering of sunlight off the atmosphere molecules. To better understand this phenomenon, it is worth considering that a large portion of solar energy is contained between the blue and red regions of the visible spectrum, where blue light (0.425 µm) has a shorter wavelength than red light (0.650 µm). Consequently, based on the above-mentioned equation, blue light scatters about 5.5 times more intensity than red light. For this reason, more blue light is scattered than red, green, and yellow, and so the sky appears blue, when viewed away from the sun’s disk. The Rayleigh scattering of unpolarized sunlight by air molecules has maxima in the forward and backward directions, whereas it shows minima in the side directions. Furthermore, the light scattered by particles is not delimited only on the incidence plane, but is visible in all the azimuthal directions. The derived scattering patterns are symmetrical in the three-dimensional space, because of the spherical symmetry assumed for air molecules.