What is meant by the term 'wavelength of light'. Radiation bands and matter Visible wavelength range
History
The first explanations of the causes of the appearance of the visible radiation spectrum were given by Isaac Newton in the book "Optics" and Johann Goethe in the work "The Theory of Colors", but even before them, Roger Bacon observed the optical spectrum in a glass of water. Only four centuries later did Newton discover the dispersion of light in prisms.
Newton first used the word spectrum (lat. spectrum - vision, appearance) in print in 1671, describing his optical experiments. He discovered that when a beam of light hits the surface of a glass prism at an angle to the surface, some of the light is reflected and some passes through the glass, forming bands of different colors. The scientist suggested that light consists of a stream of particles (corpuscles) of different colors, and that particles of different colors move in a transparent medium at different speeds. According to his assumption, red light traveled faster than violet, and therefore the red beam was not deflected on the prism as much as violet. Because of this, a visible spectrum of colors arose.
Newton divided light into seven colors: red, orange, yellow, green, blue, indigo and violet. The number seven he chose from the belief (derived from the ancient Greek sophists) that there is a connection between colors, musical notes, objects in the solar system, and the days of the week. The human eye is relatively weakly sensitive to indigo frequencies, so some people cannot distinguish it from blue or purple. Therefore, after Newton, it was often proposed to consider indigo not an independent color, but only a shade of violet or blue (however, it is still included in the spectrum in the Western tradition). In the Russian tradition, indigo corresponds to blue.
| Colour | Wavelength range, nm | Frequency range, THz | Photon energy range, eV |
|---|---|---|---|
| Violet | ≤450 | ≥667 | ≥2,75 |
| Blue | 450-480 | 625-667 | 2,58-2,75 |
| blue green | 480-510 | 588-625 | 2,43-2,58 |
| Green | 510-550 | 545-588 | 2,25-2,43 |
| yellow green | 550-570 | 526-545 | 2,17-2,25 |
| Yellow | 570-590 | 508-526 | 2,10-2,17 |
| Orange | 590-630 | 476-508 | 1,97-2,10 |
| Red | ≥630 | ≤476 | ≤1,97 |
The boundaries of the ranges indicated in the table are conditional, but in reality the colors smoothly transition into each other, and the location of the boundaries between them visible to the observer depends to a large extent on the conditions of observation.
see also
Notes
- Gagarin A.P. Light// Physical Encyclopedia: [in 5 volumes] / Ch. ed. A. M. Prokhorov. - M.: Great Russian Encyclopedia, 1994. - Vol. 4: Poynting - Robertson - Streamers. - S. 460. - 704 p. - 40,000 copies. - ISBN 5-85270-087-8.
- GOST 8.332-78. State system for ensuring uniformity of measurements. Light measurements. Values of the relative spectral luminous efficiency of monochromatic radiation for daytime vision
The electromagnetic spectrum represents the range of all frequencies or wavelengths of electromagnetic radiation from very low energy frequencies like radio waves to very high frequencies like gamma rays. Light is the part of electromagnetic radiation that is visible to the human eye and is called visible light.
The sun's rays are much broader than the visible spectrum of light and are described as a full spectrum, including the range of wavelengths needed to support life on earth and: infrared, visible, and ultraviolet (UV).
The human eye only responds to visible light, which lies between infrared and ultraviolet radiation of tiny wavelengths. The wavelength of visible light is only 400 to 700 nm (nanometer-billionth of a meter).
The visible spectrum of light includes seven color bands when the sun's rays are refracted through a prism: red, orange, yellow, green, cyan, indigo and violet.
The first person to discover that white is made up of the colors of the rainbow was Isaac Newton who, in 1666, sent a beam of sunlight through a narrow slit and then through a prism onto a wall - getting all the colors visible.
Visible light application
Over the years, the lighting industry has rapidly developed electrical and artificial sources that mimic the properties of solar radiation.
In the 1960s, scientists coined the term "full spectrum illumination" to describe sources that emit a semblance of full natural light, which included the ultraviolet and visible spectrum necessary for the health of the human body, animals and plants.
Artificial lighting for the home or office refers to natural lighting in a continuous spectral power distribution which represents the power of the source as a function of wavelength with a uniform level of radiant energy associated with and halogen lamps.
Visible light is part of electromagnetic radiation (EM), like radio waves, infrared radiation, ultraviolet radiation, X-rays, and microwaves. Generally, visible light is defined as visually detectable to most human eyes.
EM radiation transmits waves or particles at various wavelengths and frequencies. So wide the range of wavelengths is called the electromagnetic spectrum.The spectrum is generally divided into seven bands in order of decreasing wavelength and increasing energy and frequency. The generic designation represents radio waves, microwaves, infrared (IR), visible light, ultraviolet (UV), x-rays, and gamma rays.
The wavelength of visible light lies in the electromagnetic spectrum between infrared (IR) and ultraviolet (UV).
It has a frequency of 4 × 10 14 to 8 × 10 14 cycles per second, or hertz (Hz), and a vibration length from 740 nanometers (nm) or 7.4 × 10 -5 cm to 380 nm or 3.8 × 10 - 5 cmWhat is color
Perhaps the most important characteristic of visible light is explanation of what color is. Color is an inherent property and artifact of the human eye. Oddly enough, but objects "do not have" color - it exists only in the head of the beholder. Our eyes contain specialized cells that form the retina, which acts as receivers tuned to wavelengths in this narrow frequency band.
star betelgeuse
Star Rigel
Astronomers can also determine which objects are made of what, since each element absorbs light at specific wavelengths, called an absorption spectrum. Knowing the absorption spectra of elements, astronomers can use spectroscopes to determine the chemical composition of stars, gas and dust clouds, and other distant objects.
Visible radiation- electromagnetic waves perceived by the human eye, which occupy a portion of the spectrum with a wavelength of approximately 380 (violet) to 740 nm (red). Such waves occupy the frequency range from 400 to 790 terahertz. Electromagnetic radiation with these wavelengths is also called visible light, or simply light(in the narrow sense of the word). The human eye is most sensitive to light at 555 nm (540 THz), in the green part of the spectrum.
Visible radiation also enters the "optical window", a region of the spectrum of electromagnetic radiation that is practically not absorbed by the earth's atmosphere. Clean air scatters blue light a little more than longer wavelengths (toward the red end of the spectrum), so the midday sky looks blue.
Many species of animals are able to see radiation that is not visible to the human eye, that is, not included in the visible range. For example, bees and many other insects see light in the ultraviolet range, which helps them find nectar on flowers. Plants pollinated by insects are in a better position in terms of procreation if they are bright in the ultraviolet spectrum. Birds are also able to see ultraviolet light (300-400 nm), and some species even have markings on their plumage to attract a partner, visible only in ultraviolet light.
Visible spectrum
When a white beam is decomposed in a prism, a spectrum is formed in which radiation of different wavelengths is refracted at different angles. The colors included in the spectrum, that is, those colors that can be obtained by light waves of one wavelength (or a very narrow range), are called spectral colors. The main spectral colors (having their own name), as well as the emission characteristics of these colors, are presented in the table:
| Colour | Wavelength range, nm | Frequency range, THz | Photon energy range, eV |
|---|---|---|---|
| Violet | 380-440 | 790-680 | 2,82-3,26 |
| Blue | 440-485 | 680-620 | 2,56-2,82 |
| Blue | 485-500 | 620-600 | 2,48-2,56 |
| Green | 500-565 | 600-530 | 2,19-2,48 |
| Yellow | 565-590 | 530-510 | 2,10-2,19 |
| Orange | 590-625 | 510-480 | 1,98-2,10 |
| Red | 625-740 | 480-400 | 1,68-1,98 |
Light plays an important role in photography. The usual sunlight has a rather complex spectral composition.
The spectral composition of the visible part of sunlight is characterized by the presence of monochromatic radiation, the wavelength of which is in the range of 400-720 nm, according to other sources, 380-780 nm.
In other words, sunlight can be decomposed into monochromatic components. At the same time, the monochromatic (or single color) components of daylight cannot be clearly identified, and, due to the continuity of the spectrum, smoothly transition from one color to another.
It is considered that certain colors are situated in certain range of wavelengths. This is illustrated in Table 1.
Light wavelengths
Table 1
For photographers, the distribution of wavelengths over the zones of the spectrum is of particular interest.
In total there are three spectrum zones: Blue ( B lue), green ( G reen) and Red ( R ed).
By the first letters of English words R ed (red), G rein (green), B lue (blue) is called the color representation system - RGB.
AT RGB- the system operates a lot of devices connected by graphic information, for example, digital cameras, displays, etc.
The wavelengths of monochromatic radiations, distributed over the zones of the spectrum, are presented in Table 2.
When working with tables it is important to take into account the continuous nature of the spectrum. It is the continuous nature of the spectrum that leads to a discrepancy, both in the width of the visible radiation spectrum and in the position of the boundaries of the spectral colors.
Wavelengths of monochromatic radiations distributed over spectrum zones
table 2
As for monochromatic colors, different researchers allocate a different amount of them! It is customary to count from six to eight different colors of the spectrum.
Six colors of the spectrum
Table 3
When highlighting seven colors of the spectrum it is proposed from the range of blue 436-495 nm, see Table 3, to distinguish two components, one of which has a blue (440-485 nm), the other has a blue (485-500 nm) color.
Seven colors of the spectrum
Table 4
The names of the seven colors of the spectrum are given in Table 5.
Names of the seven colors of the spectrum
Table 5
When highlighting eight colors of the spectrum stand out separately yellow green(550-575 nm) by reducing the range green and yellow colors respectively.
Eight colors of the spectrum
Table 6
For various purposes, researchers can distinguish another (much larger) number of spectrum colors. However, for practical purposes, photographers tend to limit themselves to 6-8 colors.
Primary and secondary colors
Fig.1. Black and white, primary and secondary colors
Primary colors- it three colors from which you can get any other colors.
Actually, modern digital photography is based on this principle, using red (R), green (G) and blue (B) as primary colors, see Table 7.
Additional colors are colors that, when mixed with primary colors, produce white. see Table 7.
Table 7
Main color |
Complementary color |
Resulting Color |
RGB (0 0 225) |
RGB (255 225 0) |
RGB (255 225 225) |
RGB (0 225 0) |
RGB (255 0 225) |
RGB (255 225 225) |
RGB (255 0 0) |
RGB (0 225 225) |
RGB (255 225 225) |
1. FEATURES OF COLOR PERCEPTION.
It is now known that color is a person's representation of the visible part of the electromagnetic radiation spectrum. Light is perceived by photoreceptors located at the back of the pupil. These receptors convert electromagnetic radiation energy into electrical signals. The receptors are concentrated mostly in a limited area of the retina or retina called the fovea. This part of the retina is able to perceive image details and color much better than the rest of it. With the help of the eye muscles, the fossa is displaced so as to perceive different parts of the environment. A field of view in which details are well distinguished and color is limited to approximately 2 degrees.
There are two types of receptors: rods and cones. The rods are only active in extremely low light conditions (night vision) and are of no practical importance in the perception of color images; they are more concentrated along the periphery of the field of view. The cones are responsible for color perception and they are concentrated in the fovea. There are three types of cones that sense long, medium, and short wavelengths of light.
Each type of cone has its own spectral sensitivity. It is approximately believed that the first type perceives light waves with a length of 400 to 500 nm (conditionally "blue" color component), the second - from 500 to 600 nm (conditionally "green" component) and the third - from 600 to 700 nm (conditionally " red "component). Color is perceived depending on the wavelength and intensity of the light present.
The eye is most sensitive to green rays, the least to blue. It has been experimentally established that among radiations of equal power, the greatest light sensation is caused by monochromatic yellow-green radiation with a wavelength of 555 nm. The spectral sensitivity of the eye depends on the ambient light. At dusk, the maximum spectral luminous efficiency shifts towards blue radiation, which is caused by the different spectral sensitivity of rods and cones. In the dark, blue has a greater effect than red, with equal radiation power, and in the light - on the contrary.
Different people perceive the same color differently. Perception of colors changes with age, depends on visual acuity, mood and other factors. However, such differences relate mainly to subtle shades of color, so in general it can be argued that most people perceive primary colors in the same way.
2. WHAT IS COLOR?
What is color? Physics views light as an electromagnetic wave. A wave is simply a change in the state of a medium or field propagating in space at some speed. Any wave has a length - this is the distance between the crests of the wave.
Those wavelengths that the human eye is able to perceive is called visible light. For example, we perceive light with the longest wavelength as red, and light with the shortest wavelength as violet. At the same time, it is worth noting that our ear also perceives waves, only of a very large wavelength and of a slightly different nature. Sound is the vibration of matter. For example, in a vacuum there are no particles of matter (for example, air). And there is no sound, the sound wave does not propagate in a vacuum.
The unit of measurement of the wavelength of the optical region of the radiation spectrum is nanometer (nm);
1 nm = 1 x 10 -3 microns (micron) = 1 x 10 -6 mm (millimeters).
The colors we perceive vary depending on the wavelength of visible light:
Colour |
Wavelength, nm |
Red |
from 620 to 760 |
Orange |
from 585 to 620 |
Yellow |
from 575 to 585 |
Green |
from 510 to 575 |
Blue |
from 480 to 510 |
Blue |
from 450 to 480 |
Violet |
from 380 to 450 |
The order of the arrangement of colors is easy to remember by the abbreviation of words: every hunter wants to know where the pheasant sits.
There is no sharp border between the colors, but white is missing among the above colors ...
The thing is that no specific wavelength corresponds to white light. However, the boundaries of the ranges of white light and its constituent colors are usually characterized by their wavelengths in vacuum. Thus, white light is a complex light, a set of waves with lengths from 380 to 760 nm.
The reason why a person is able to see light is due to the effect of light of certain wavelengths on the retina of the eye.
When light passes through a substance that has a refractive angle, the light is decomposed into its constituent colors, while both the speed and wavelength change, and the frequency of light oscillations remains unchanged.
Light with wavelengths longer than the longest in the visible light spectrum (red) is called infrared ( from the Latin word infra - below; that is, below that part of the spectrum that the eye can perceive). And light with wavelengths shorter than the shortest in the visible spectrum is called ultraviolet (from the Latin word ultra - more, over; that is, a wavelength higher than that which the eye can perceive).
Neither infrared nor ultraviolet light is accessible to the human eye, as well as many other types of waves. However, we can perceive a huge range of different colors (waveband).
3. COLOR HARMONY.
In color theory, the color wheel contains all colors visible to humans, from purple to red. The color wheel shows how colors are related to each other, and allows you to determine the harmonious combinations of these colors according to certain rules.
Black, white and gray are not marked on the color wheel because, strictly speaking, they are not colors. These are neutral tones.
3.1. Color combinations.
The color schemes show harmonious combinations of colors. Note that colors can and should be varied in saturation and lightness (brightness). And by the way, another harmony that is often found: by saturation. The picture shows the possible options for color harmony.
Do not apply colors in equal amounts. Make one color better as a background, and let the other just be an accent on it. Interestingly, when mixed, complementary colors give a gray color (three primary colors, by the way, too). Therefore, if you apply them side by side and in large quantities, then the viewer's eyes will blend to gray!
You can experiment with this using color picker .
4. SENSING OF DEPTH.
An important role in creating a color composition is played by the division of colors into warm and cold. This division is easy to see on the color wheel (see pictures above). On this circle stands out "warm" red-yellow area and "cold" blue area separated by a vertical line. This division is difficult to explain at the level of physics - the division into "two camps" occurs, rather, at the subconscious level.
Since childhood, we have become accustomed to the fact that the sun, fire, corners and all heat sources have red and yellow shades, and snow, water, sky - blue-blue and blue-green shades. This is fixed in our subconscious, and dictates to us the perception of color. But there are also "violators" of this division. So, the light beige moon, burgundy colors are cold colors, and the light blue glow of heated bodies has a warm color.
Bright, warm colors create the effect of movement towards the viewer and appear closer. Warm colors attract attention and are well suited to highlight important elements of the publication.
cold colors appear to move away and create the effect of moving away from the viewer. In combination cold colors can cause a feeling of alienation and isolation, or, on the contrary, be calming and encouraging.
The movement effect caused by the combination of warm and cold colors is used by designers. For the background they choose cold shades, and warm for objects in the foreground. So, if you look at photos taken at presentations and press conferences, you will see speakers in front of a blue background. Such a background gives significance and importance to the figure of the speaker. This technique can be recommended to novice designers.
As a rule, color solutions based on the dominance of a cold or warm range of colors work better, and not on a uniform mixture of shades. At the same time, in combinations dominated by warm tones, to decorate selections and enhance contrastcan be used cold shades, and vice versa.
