Revealing the secrets of light. Principles of Huygens Fresnel

Light phenomena are so ordinary for us that, perceiving their various manifestations, we do not even think about the essence of the processes that are taking place. The share of information received by the human brain through precisely the light phenomena reaches ninety percent, which indicates their enormous role in our life activity. The richness of the colors of the world around us, the blue tint of the sky, the rainbow, our own reflection in the mirror, are the subject of the description rather for people who are lyrical than those with a scientific mindset. But among the scientists and naturalists who are striving to penetrate into the essence of the surrounding objects and phenomena, to make their quantitative measurement and qualitative assessment, there were many willing to reveal the secret of light.

The first researchers of light phenomena, whose works have reached our days, knew about the properties of curved surfaces. Euclid (300 BC) and Ptolemy (127-151) were able to describe the laws of geometric optics, but they already received practical application much later in the constructions of the first glasses (1285), telescopes (1450) , Microscopes (1595).

Further investigation of the light phenomena made it necessary to go from geometrical optics to the wave theory of light, the description of which is known to us as the Huygens-Fresnel principles. Huygens was the first to question Newton's theory and suggested that the light ray be viewed not as a stream of the smallest rapidly spreading particles, but as a wave. The Huygens wave theory not only fully confirmed the laws of geometric optics, but also allowed a new look at all the light phenomena. Taking as a basis the expression that every point of the environment in which the wave propagates is inherent in the property of becoming a source of secondary waves, was able to explain the Huygens principle of the law of light reflection and other phenomena previously described by Newton's theory. But the concept of diffraction could not be explained in any way by the principles of the new theory, and there were so many supporters of Newtonian views that the arguments about the true nature of light were dragged on for a hundred years.

The Huygens-Fresnel principle explains the concept of "diffraction of light" by determining its dependence on the wavelength. The sound behind the wall we hear, the light does not go around the obstacle, but gives a shadow. But the Huygens-Fresnel principles do not refute this example. Diffraction is inherent in light waves, but it is so invisible because of the meager size of the length of the light wave that it was impossible to fix it, and only Frenell was able to describe this phenomenon, he was also able to calculate the wavelength of a light wave that is half a micron (half a thousandth of a millimeter) .

Having made a significant contribution to the development and proof of the truth of the wave theory of light in the nineteenth century, Fresnel is rightfully considered one of its founders. His name entered the history of world science, and the foundations of the theory, laid down in the seventeenth century by Huygens, are usually called the "Huygens-Fresnel principles."

Briefly summarizing, the advantages of Huygens' wave theory of light lie in the explanation of many phenomena to which the Newtonian version of the nature of light does not give an explanation. The superposition of light waves leads to the phenomenon of interference, darkened areas in the form of Newton's rings the great scientist himself could not explain. After all, according to his theory, the superposition of light streams should be accompanied by an increase in their strength. And the manifestation of diffraction in a light wave was able to confirm by his experiments Fresnel, than completely dispelled doubts in the wave nature of light.

A new look at the properties of the light beam, based on the principles of Huygens-Fresnel, gave impetus to the development of scientific and technical thought. As a result, we witnessed the emergence of such an invention as a laser (60s of the 20th century), which became a powerful tool in the hands of scientists, physicians, technologists. Photographers have the opportunity to create their masterpieces using optical filters, astronomers can study the composition of distant stars at a distance, and many other areas of human life enriched with the appearance of new views on the nature of the ordinary light beam.