Diffraction of light: frequently asked questions

Light has always been mysterious and attractive to man. He was associated with higher forces. Light gave life - and people understood it from the most ancient times. The proof of this is the cults of the light source - the Sun. Therefore, all the phenomena that a person could not explain on the basis of the knowledge that he had, occupied him immensely. One of those phenomena that an attentive person usually notices is the diffraction of light. What is it?

You can see the phenomenon with your own eyes if you miss a ray of light through a narrow hole and look at the spot of light that passed through it. We will see that around the border - alternating dark and light stripes. Why do we see just such a picture?

The fact is that waves at some points around the spot intensify each other, and in some, on the contrary, are in phase opposition, and therefore extinguish each other. The specific geometric parameters of the resulting pattern depend on the wavelength (therefore, for the waves of red and green light there will be a different diffraction pattern) and the diameter of the light beam. It becomes conical from cylindrical. This is the diffraction of light. And the very phenomenon of interaction of waves is called interference. Such a phenomenon occurred in the 19th century. Interference and diffraction of light are phenomena that are most often described in textbooks of physics.

What is the practical application of this physical phenomenon? It is taken into account when creating optical instruments (cameras, microscopes, telescopes), because they all have a lens that limits the light beam to its frame.

Distinguish between diffraction in the near zone (the point at which a particular beam falls is close to an obstacle). This phenomenon is called Fresnel diffraction. But if the diffraction occurs in the far zone (the interacting rays are almost parallel), the physicist calls it Fraunhofer diffraction. It has a curious property: if the hole is large enough, the diffraction will remain invisible.

Also in the textbook of physics we come across the term diffraction grating. What it is? Optical device, which is a transparent or reflective plate with applied parallel strokes. When white light passes through it , one can see the separation of light into a spectrum. Yes, the grid becomes painted in the colors of the rainbow. The prism gives only one spectrum, and the lattice - a few. He is not alone, because the light is split into beams formed by different bands, and the spectra are the longer the larger the angle of deviation of radiation from the original direction.

However, you can pass through the grate not only white light. And also the light passed through some substance. This procedure is called spectral analysis and makes it possible to reveal the composition of the samples under study. By what rays were left after passing through the diffraction grating, it is possible to identify what the researcher is dealing with.

And you also saw a diffraction grating, exactly, you saw it. Doubt? This was when you last held a disk for your computer. And he played beautifully with all the colors of the rainbow. You observed, without knowing it, the phenomenon of diffraction of light. The areas on the disc on which the data is recorded are microscopic in size (so the disk is so sensitive to damage), and the recording is done in a circle, so the surface of the laser disc is a continuous diffraction grating.

However, let us consider the phenomenon of diffraction more closely. And find out what the diffraction of light is, if we explain it in plain language. So, if the rays meet with an impenetrable obstacle, then the rays passing next to this edge do not go straight, the waves seem to go around the obstacle that they encountered on the way. Thanks to this process, the wave is able to completely bend around objects that are no larger than its length.

Good luck in studying physics!