What is light?

Every day we see the light of day. But what is light? Ancient scholars thought that from the human eye, animals and other creatures go special thin tentacles and with help palpation of objects of the eye sees them. A more plausible hypothesis about the nature of light put forward 2500 years ago Pythagoras. He believed that every object constantly emits in all directions fine particle flows that getting into the eye, causing a sensation of light, or the outlines of objects.

Every day we see the light of day. But what is light?

Around the question, what is light, there was a real scientific debate in the 17th century between the corpuscular and wave theories of the nature of light. The first is connected with the name of Isaac Newton, and the second - Christian Huygens.

Newton held the corpuscular theory, according to which the light - a stream of particles (corpuscles), coming from the source in all directions. If they come an eye, the latter perceives these particles as the light.

What is the light according to the ideas of Huygens? This flow of the waves are distributed in an unknown, hypothetical environment - ether, which filling all around. This ether penetrates into things - air, glass, water. It fills the vast space between the stars, planets and other celestial bodies.

Both of these theories or hypotheses exist in parallel, and none of them could not win a decisive victory. But Newton was able to persuade the majority of scientists on his side. Discovery of the law of inertia explained perfectly straight flight "light" with help movement particle from inertia. Reflected light from the mirrors is quite consistent with the elastic rebound of balls in their impact on plane. However, Newton could not explain why these particles do not collide in space, if the light beams intersect. The wave theory explained it perfectly. The waves, at least on the surface of water, pass freely through each other without causing mutual interference.

The dual position in the views on the nature of light lasted until the 19th century, when the data on the theory of wave processes, led scientists to recognize that light behaves like a wave. Especially tried this Scottish scientist John. C. Maxwell (1831-1879). He proved that light - is electromagnetic waves, which, incidentally, extend well into the void, and do not need any "ether".

However, the wave theory of light could not explain, for example, a photo, or the photoelectric effect - the ability of light "pull" from the metal special particles - electrons.

Deadly attack on electromagnetic wave theory of light struck in the late 19th century, the so-called "ultraviolet". The fact that, according to this theory, any body must continuously radiate energy into the space, and consequently cooled, and down to absolute zero. And since all frequencies are emitted, including a very energy-intensive - ultraviolet, and the catastrophe of "global" cooling of the bodies has been called "ultraviolet catastrophe".

But if this does not occur in nature, it follows that the electromagnetic wave nature of light is meaningless. Exiting the "UV" impasse was found by the German physicist Max Planck (1858-1942). He suggested that the energy of electromagnetic radiation is allocated not continuously, but in portions, called quanta. And it turned out that at high frequencies (ultraviolet range), these rays are so great, and their creation is expended so much energy that of energy on the radiation no longer suffices. Therefore, the radiation energy is almost zero, and "ultraviolet catastrophe" does not threaten us at high frequencies.

The quantum hypothesis explained well and the phenomenon of the photoelectric effect and the chemical action of light, including photosynthesis and more. The resulting "symbiosis" has two hypotheses to explain all of the properties of electromagnetic radiation, including light.

And we got the following:

- In the propagation of light behaves more like a wave, and in the event of absorption - rather like particle;

- At high frequencies, the main role is played by quantum ("corpuscular") properties of light, and for small - wave.