Use of wave properties of light. Diffraction grating

The wave nature of light has been proven long ago. To solve practical problems, the principles of geometrical optics are often used, but also the wave properties of light are widely used in the most diverse branches of modern science and technology. An example of this is diffraction. The ability of a wave to envelop obstacles that are encountered in its path is inherent in light. This phenomenon is manifested when the waves fall into the region of the so-called geometric shadow. An explanation of the phenomenon of diffraction gives the Huygens principle. According to this explanation, each point in the path of the wave becomes the center for the secondary waves. In the envelope of these waves, the position of the wavefront is set for each next time moment.

In the example with a plane wave normally incident on an opening made in an opaque screen, according to Huygens theory, each point that is emitted by the opening of the wavefront section has the ability to become a source of secondary waves (in a homogeneous isotropic medium they are spherical).

It is sufficient to construct the envelope of the secondary waves at a certain time, in order to easily trace the phenomenon of the wave enveloping the edge of the hole. This is explained by the fact that the front of the wave enters the region of the so-called geometric shadow.

The use of the diffraction property has found wide application in a device called the diffraction grating. In his initial experiments with diffraction of light James Gregory used an ordinary bird's feather. Later it was replaced by a specific optical device. Diffraction grating is a set of a significant number of strokes arranged on a certain surface regularly arranged. They can be either slits or projections, depending on the type to which the particular diffraction grating belongs.

There are two types of grids - reflective and transparent. The first include devices that use a reflective surface with applied strokes. The latter use transparent surfaces, both streaks and slits can be used here.

The principle of the action of the diffraction grating is explained directly by the wave properties of light. To break the front of a light wave, the gratings are used. As a result, individual beams of so-called coherent light are formed. Having undergone diffraction on strokes, they interfere with each other. Taking into account the fact that waves of different length create maximum interference at completely different angles (determined by the path difference for the interfering beams), a white light spread out into the spectrum is obtained at the output.

Diffraction grating as a device finds application in the most diverse spheres of human life activity. It is used in spectral instruments, both as optical sensors for angular (linear) displacements, and as polarizers or as infrared radiation filters. Also, it can be beam dividers for interferometers or glasses of "anti-glare" glasses.

There is also a diffraction grating for X-rays. It was technically impossible to create it. To solve this problem, scientists have gone the original way. Crystalline lattices of some crystals are used for the decomposition of x-rays.

As the main characteristic, the resolving power of the diffraction grating is considered. It is the total number of lines in the lattice, which is multiplied by the order of the beam maximum. This expression can still be represented as the statement that for the frequency difference, the equality with the reciprocal of the difference in the time intervals of the passage of the most extreme rays, called interfering, is characteristic.

In everyday life, a compact disc or a gramophone record can serve as an illustrative example of a diffraction grating. But for the manufacture of industrial instruments high-tech equipment is used, which has high accuracy.