If you look at the sky on a cloudless autumn day, then the shining bright blue dome of the sky will not leave anyone indifferent. What explains such an amazing color? Its reason lies in three aspects - refraction, scattering and polarization. In today's work we will talk about what is the polarization of light.
Light is one of the varieties of electromagnetic radiation, therefore it is characterized by a source and directivity. In addition, we should not forget about its dual nature: in one case it, as already mentioned, is a wave, and in another - a particle (photon). Light polarization is one of the properties of any radiation in the optical range. With polarization, the oscillations of the particles of the light beam directed to the transverse surface are carried out in the same plane. Other components are cut off.
It is easiest to understand by example what polarization of light is. Imagine a long rope located horizontally between two points. The rope passes through a vertical slot in the shield plate. If now you pick it up from one end and form waves, then they will reach the opposite end only if they are created coaxially with the gap in the shield, i.e. vertically. When you try to move the rope horizontally (left-right), the waves will be extinguished, barely reaching the shield, as they will not “squeeze” across the gap. In this example, the rope is electromagnetic radiation, the shield is transparent (or translucent), and the gap is a specific property of the medium.
Since light is an electromagnetic wave, it depends on the electric and magnetic vectors of tension. They are always perpendicular to each other and, in addition, form a conditional plane perpendicular to the propagation line of the wave itself. By the way, circular polarization of light occurs when the vectors of magnetic induction and electric field rotate relative to the direction of the light beam. In turn, when a vector of electric field strength fluctuates in the same plane, a plane-polarized electromagnetic wave arises. Its second name, reflecting the same process, is “linearly polarized”.
Interestingly, the radiation from an atom of a single quantum of light is always polarized. At the same time, the luminous flux of a light bulb, the Sun, candles, a flashlight, etc. is unpolarized. This is due to the fact that the radiation comes from many atoms in which the polarization is different. Accordingly, the total flow loses its orientation. The polarization of light to a large extent depends on the characteristics of the substance or the arrangement of atoms in its crystal lattice (for solids, for example, transparent crystals). By the way, the first experiments were performed with crystals, and only subsequently, scientists drew attention to gaseous media (atmosphere). It is easy to understand that the polarization of light also depends on the location of the observer (sensor, photocell, etc.). Thus, with an increase in the angle between the direction of light from the source and the vector indicating the directivity of the line of sight, the polarization increases. If the directions are parallel, then under ideal conditions there is no polarization.
There is also a third option - a partially polarized stream of light. This configuration occurs when oscillations of the electric field or magnetic induction (their vectors) predominate.
A curious fact: the human eye can easily distinguish between wavelength (color aspect of light) and intensity, but registration of polarization is available indirectly. At the same time, many insects with faceted eyes perfectly distinguish wave polarization. It is believed that this helps them navigate.