Nature gave a person the joy of color perception: we see everything around us in a variety of colors and shades and do not even think about what could be otherwise.
Scientists argue that many animals do not distinguish colors or see them differently than humans. But what is color in terms of physics? The question is not as simple as it seems at first glance.
What is color in physics?
From the point of view of physics, different colors of objects do not exist by themselves. They are felt by us only due to different wavelengths of electromagnetic radiation waves reflected and absorbed by surfaces in the range of visible light. Each color of the spectrum corresponds to its own frequency range, but only the perception of our visual organs and the transformation of visual impulses by the brain creates a bright color picture.
When a white light beam falls on an object, most of its constituent light waves are absorbed by the surface, and only a certain part, which is in a certain range, is reflected. We perceive light waves of this range as a color inherent in an object. In fact, the color of objects appears only when light hits them.
Let’s remember the popular saying: “At night all cats are gray.” When there is not enough light, the eye cannot distinguish color ranges in the reflected waves, and all objects appear gray or black.
Nuances of terminology
If we talk about colors from the point of view of physics, then we are talking about electromagnetic waves, the length of which lies in the range from 0.1 Angstrom to about 105 Angstrom. This range is perceived by our organs of vision and is what we call visible light.
However, in popular science, and sometimes in scientific literature, it is often about the colors and color perception of monochromatic or narrow-band electromagnetic radiation in the above range. At the same time, as a rule, not the problem of color perception is discussed, but the properties inherent in electromagnetic radiation, regardless of how it is perceived by our organs of vision.
The difference between the visible and invisible portions of the full spectrum of electromagnetic waves is primarily quantitative rather than qualitative. Visible radiation with a wavelength in the range from 400 to 700 nm differs little in its characteristics from thermal radiation, the wavelengths of which lie in the range from 1000 to 2000 nm, but the former is perceived by us as light, and the latter as heat.
In practice, there are such areas of physics as optics, which mainly studies the properties of the visible range of radiation, and thermal energy, the subject of which is mainly the thermal range of electromagnetic waves.
We are able to perceive electromagnetic waves, the wavelengths of which are distributed between 380 nm (corresponding to deep violet) and 730 nm (corresponding to red). But on both sides of this range, there are radiations that the human eye does not perceive.
Waves shorter than 380 nm we call ultraviolet, and those longer than 730 nm – infrared. Many insects and some animals, such as bats, can perceive ultraviolet radiation. Sometimes people can also see a wider spectral picture due to the peculiarities of their visual organs.
There are electromagnetic waves that are shorter than ultraviolet – these are X-rays and gamma rays. As you know, even high doses of ultraviolet light are harmful to humans. Radiation with a wavelength of less than 100 nm is deadly in high doses. In the natural environment, we are reliably protected from these waves coming to us from outer space, shielding the ozone layer.
Waves longer than 2000 nm, i.e. lies outside the thermal infrared range, called radio waves. Their length can range from a few millimeters to hundreds and thousands of kilometers. Short radio waves are used in mobile telephony, household microwave ovens, and other appliances. Thanks to the use of long waves, radio communication functions.
Color perception and color blindness
So, colors are the reflected radiation of electromagnetic waves that lie in a very narrow range of lengths. There are people who have a disturbed normal color perception mechanism. They are called color blind, and for some reason they cannot see part of the normal visible spectrum.
Their perception of colors is shifted either towards the red part of the spectrum (the perception of violet and blue is deteriorated), because towards the blue part (the perception of red is deteriorated). Color blindness can be hereditary or due to retinal trauma, age-related changes, or disease.