If you look around the space in which we are, you can find familiar objects. Even bright colors on various objects seem to be something common to us. In fact, our eye is not able to form a picture of the surrounding reality, and vision is a much more subtle and complex process. First, the smallest light particles (photons), reflecting from objects, fall on the retina of the eye.
And then about 126 million light-sensitive cells send this information to the brain for processing. There, information is instantly decrypted depending on the direction of refraction and the energy of the photons. And only then it all adds up to a single picture containing a variety of shapes and shades.
Visual threshold of human vision
Of course, vision has its limits. For example, our eyes cannot see radio waves or tiny bacteria. This is only possible with special devices. How can we determine the boundary beyond which natural vision becomes impotent? Modern scientific advances in biology and physics will help answer this question. Scientists believe that any visible object has a certain visual threshold. Under certain conditions, our eye ceases to perceive familiar objects.
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Based on ability to distinguish colors
The simplest example for detecting the limit of human vision is the ability to distinguish colors. We distinguish similar colors and shades in gamut, for example violet and purple, using the wavelength of photons falling on the retina. The light-sensitive cells inside the eye are divided into two types: the so-called rods and cones.
If the first type is responsible for the perception of color in the daytime, then the second allows us to distinguish light gray shades at night or in dim lighting. Both types of cells contain receptors. They absorb energy and send signals to the brain. Well, then a picture is formed, and we can easily distinguish violet from magenta.
Clear gradation of eye cells
But that's not all. Cones, in turn, are also divided into types, and there are three of them. A certain number of receptors (opsins) are "assigned" to each of the species. They have different sensitivity to photons and are able to detect a specific range of light waves. So the S-type cones are sensitive to the violet-blue gamut of the color spectrum, which is considered to be shortwave. The M-type is responsible for the yellow-green color palette (mid-wave), and the L-type is able to distinguish between yellow and red colors (long wavelengths). Both waves and their combinations allow us to distinguish the entire rainbow spectrum, which includes up to one hundred shades.
Narrow wavelength range
There are many photons in nature, but eye cells are capable of capturing wavelengths in a negligible range (380 to 720 nanometers). This range is considered to be the spectrum of natural vision. All indicators outside this threshold cannot be recorded by the human eye. So, for example, below this threshold are the radio spectrum and infrared radiation, and above the ultraviolet and X-ray spectra, as well as gamma radiation.
The ability to distinguish between ultraviolet waves
Sometimes people can go beyond the "permissible" and catch the reflection of photons of ultraviolet radiation. This becomes possible due to the absence of the eye lens in pathologies or after surgery. If in a healthy eye the lens acts as a blocker of the ultraviolet range (try to look at the sun and you will not succeed), then people with the indicated visual defect acquire the ability to expand the range of perception of light waves up to 300 nanometers. It is curious that ultraviolet radiation in this case is transformed into a blue-white spectrum.
Can the eye pick up infrared photons?
In one of the latest studies, it was proven that in some way we can capture infrared radiation. It is only necessary to observe a certain condition: so that two infrared photons simultaneously hit the same cell of the retina. Scientists have found that in this case, the energy of the photons is added up, falling within the visible range. So, for example, radiation of 1000 nanometers is converted into 500 nanometers, and a person perceives the infrared wave as a cool cool green color.