In nature, there are no flowers as such. Each shade that we see is set by one or another wavelength. formed under the influence of the longest wavelengths and is one of the two faces of the visible spectrum.
On the nature of color
The appearance of a particular color can be explained by the laws of physics. All colors and shades are the result of brain processing of information coming through the eyes in the form of light waves of various wavelengths. In the absence of waves, people see, and with a simultaneous exposure to the entire spectrum - white.
The colors of objects are determined by the ability of their surfaces to absorb waves of a certain wavelength and repel all others. Lighting also matters: the brighter the light, the more intense the waves are reflected, and the brighter the object looks.
Humans are able to distinguish over one hundred thousand colors. Favorite by many scarlet, burgundy and cherry shades are formed by the longest waves. However, for the human eye to see red, it must not exceed 700 nanometers. Beyond this threshold, the infrared spectrum, invisible to humans, begins. The opposite boundary separating the violet hues from the ultraviolet spectrum is at a level of about 400 nm.
Color spectrum
The spectrum of colors, as some of their totality, distributed in ascending order of wavelength, was discovered by Newton during his famous experiments with a prism. It was he who singled out 7 clearly distinguishable colors, and among them - 3 main ones. Red color refers to both distinguishable and basic. All the shades that people distinguish are the visible region of the vast electromagnetic spectrum. Thus, color is an electromagnetic wave of a certain length, not shorter than 400, but not longer than 700 nm.
Newton noticed that beams of light of different colors had different degrees of refraction. To put it more correctly, the glass refracted them in different ways. Max Speed the passage of rays through the substance and, as a result, the smallest refraction was facilitated by the largest wavelength. Red is the visible representation of the least refracted rays.
Waves forming red
An electromagnetic wave is characterized by such parameters as length, frequency, and Under the wavelength (λ), it is customary to understand the smallest distance between its points that oscillate in the same phases. Basic units of wavelength:
- micron (1/1000000 meters);
- millimicron, or nanometer (1/1000 micron);
- angstrom (1/10 millimicron).
The maximum possible wavelength of red is 780 microns (7800 angstroms) when passing through a vacuum. The minimum wavelength of this spectrum is 625 microns (6250 angstroms).
Another significant indicator is the frequency of oscillations. It is related to the length, so the wave can be set to any of these values. The frequency of red waves is in the range from 400 to 480 Hz. The photon energy in this case forms a range from 1.68 to 1.98 eV.
red color temperature
Shades that a person subconsciously perceives as warm or cold, with scientific point vision, as a rule, have the opposite temperature regime. The colors associated with sunlight - red, orange, yellow - are usually considered warm, and the opposite colors are considered cold.
However, radiation theory proves the opposite: red shades are much lower than blue ones. In fact, this is easy to confirm: hot young stars have and fading - red; when heated, the metal first turns red, then yellow, and then white.
According to Wien's law, there is an inverse relationship between the degree of wave heating and its length. The more the object heats up, the more power falls on radiation from the short wave region, and vice versa. It remains only to remember where in the visible spectrum there is the largest wavelength: red takes a position that contrasts with blue tones, and is the least warm.
shades of red
Depending on the specific value that the wavelength has, the red color takes on various shades: scarlet, raspberry, burgundy, brick, cherry, etc.
Hue is characterized by 4 parameters. These are such as:
- Hue is the position that a color occupies on the spectrum among the 7 visible colors. The length of the electromagnetic wave sets the tone.
- Brightness - is determined by the strength of the radiation of energy of a certain color tone. The maximum decrease in brightness leads to the fact that a person will see black. With a gradual increase in brightness, it will appear behind it - burgundy, after - scarlet, and with a maximum increase in energy - bright red.
- Lightness - characterizes the proximity of the shade to white. White color is the result of mixing waves of different spectra. With a successive build-up of this effect, the red color will turn into crimson, then pink, then light pink and finally white.
- Saturation determines how far a color is from gray. Gray color by its nature is the three primary colors mixed in different amounts when the brightness of the light emission is reduced to 50%.
The electromagnetic spectrum is conditionally divided into ranges. As a result of their consideration, you need to know the following.
- Range name electromagnetic waves.
- The order in which they follow.
- Range boundaries in wavelengths or frequencies.
- What causes the absorption or emission of waves of one or another range.
- The use of each type of electromagnetic waves.
- Sources of radiation of various electromagnetic waves (natural and artificial).
- Danger of every kind of waves.
- Examples of objects that have dimensions comparable to the wavelength of the corresponding range.
- The concept of black body radiation.
- Solar radiation and atmospheric transparency windows.
Ranges of electromagnetic waves
microwave range
Microwave radiation is used to heat food in microwave ovens, mobile communications, radars (radar), up to 300 GHz easily passes through the atmosphere, therefore it is suitable for satellite communications. Radiometers for remote sensing and determining the temperature of different layers of the atmosphere, as well as radio telescopes, operate in this range. This range is one of the key ranges for EPR spectroscopy and rotational spectra molecules. Prolonged exposure to the eyes causes cataracts. Mobile phones negatively affect the brain.
A characteristic feature of microwave waves is that their wavelength is comparable to the size of the equipment. Therefore, in this range, devices are designed on the basis of distributed elements. Waveguides and strip lines are used for energy transmission, and cavity resonators or resonant lines are used as resonant elements. Man-made sources of MW waves are klystrons, magnetrons, traveling wave tubes (TWTs), Gunn diodes, and avalanche transit diodes (ATDs). In addition, there are masers, analogues of lasers in the long wavelength ranges.
Microwave waves are emitted by stars.
In the microwave range is the so-called cosmic background microwave radiation (relic radiation), which in its spectral characteristics fully corresponds to the radiation of a blackbody with a temperature of 2.72K. The maximum of its intensity falls at a frequency of 160 GHz (1.9 mm) (see figure below). The presence of this radiation and its parameters are one of the arguments in favor of the theory big bang, which is currently the basis of modern cosmology. The last one, according to these measurements and observations in particular, occurred 13.6 billion years ago.
Above 300 GHz (shorter than 1 mm), electromagnetic waves are very strongly absorbed by the Earth's atmosphere. The atmosphere begins to be transparent in the IR and visible ranges.
| Colour | Wavelength range, nm | Frequency range, THz | Photon energy range, eV |
|---|---|---|---|
| Violet | 380-440 | 680-790 | 2,82-3,26 |
| Blue | 440-485 | 620-680 | 2,56-2,82 |
| Blue | 485-500 | 600-620 | 2,48-2,56 |
| Green | 500-565 | 530-600 | 2,19-2,48 |
| Yellow | 565-590 | 510-530 | 2,10-2,19 |
| Orange | 590-625 | 480-510 | 1,98-2,10 |
| Red | 625-740 | 400-480 | 1,68-1,98 |
Among the lasers and sources with their application, emitting in the visible range, the following can be mentioned: the first launched laser, - ruby, with a wavelength of 694.3 nm, diode lasers, for example, based on GaInP and AlGaInP for the red range, and based on GaN for the blue range, titanium-sapphire laser, He-Ne laser, argon and krypton ion lasers, copper vapor laser, dye lasers, lasers with frequency doubling or frequency summation in nonlinear media, Raman lasers. (https://www.rp-photonics.com/visible_lasers.html?s=ak).
For a long time there was a problem in creating compact lasers in the blue-green part of the spectrum. There were gas lasers, such as the argon ion laser (since 1964), which has two main generation lines in the blue and green parts of the spectrum (488 and 514 nm), or the helium-cadmium laser. However, they were not suitable for many applications due to their bulkiness and the limited number of generation lines. Create semiconductor lasers with a wide bandgap failed due to huge technological difficulties. However, eventually developed effective methods doubling and tripling the frequency of solid-state lasers in the IR and optical range in nonlinear crystals, semiconductor lasers based on double GaN compounds and lasers with an increase in the pump frequency (upconversion lasers).
Light sources in the blue-green region make it possible to increase the recording density on a CD-ROM, the quality of reprographics, are necessary for creating full-color projectors, for communicating with submarines, for removing the relief of the seabed, for laser cooling of individual atoms and ions, for controlling deposition from gas (vapor deposition), in flow cytometry. (taken from “Compact blue-green lasers” by W. P. Risk et al).
Literature:
UV range
It is believed that the ultraviolet range occupies the region from 10 to 380 nm. Although its boundaries are not clearly defined, especially in the shortwave region. It is divided into sub-ranges and this division is also not unambiguous, since in different sources it is tied to various physical and biological processes.
So on the website of the "Health Physics Society" the ultraviolet range is defined within the limits of 40 - 400 nm and is divided into five subranges: vacuum UV (40-190 nm), far UV (190-220 nm), UVC (220-290 nm), UVB (290-320 nm), and UVA (320-400 nm) (black light). In the English version of the Wikipedia article on ultraviolet "Ultraviolet", the range of 40 - 400 nm is allocated to ultraviolet radiation, however, in the table in the text it is divided into a bunch of overlapping subranges, starting from 10 nm. In the Russian-language version of Wikipedia "Ultraviolet radiation" from the very beginning, the limits of the UV range are set within 10 - 400 nm. In addition, Wikipedia for the UVC, UVB and UVA ranges indicates the areas 100 - 280, 280 - 315, 315 - 400 nm.
Ultraviolet radiation, despite its beneficial effect in small quantities on biological objects, is at the same time the most dangerous of all other natural widespread radiations of other ranges.
The main natural source of UV radiation is the Sun. However, not all radiation reaches the Earth, since it is absorbed by the ozone layer of the stratosphere and, in the region shorter than 200 nm, is very strongly absorbed by atmospheric oxygen.
UVC is almost completely absorbed by the atmosphere and does not reach earth's surface. This range is used by germicidal lamps. Overexposure results in corneal damage and snow blindness, as well as severe facial burns.
UVB is the most damaging part of UV radiation as it has enough energy to damage DNA. It is not completely absorbed by the atmosphere (about 2% passes). This radiation is necessary for the production (synthesis) of vitamin D, but the harmful effects can cause burns, cataracts and skin cancer. This part of the radiation is absorbed by atmospheric ozone, the decline of which is a cause for concern.
UVA almost completely reaches the Earth (99%). It is responsible for sunburn, but excess leads to burns. Like UVB, it is necessary for the synthesis of vitamin D. Excessive exposure leads to immune system suppression, skin stiffness, and cataract formation. Radiation in this range is also called black light. Insects and birds are able to see this light.
The figure below shows, for example, the dependence of ozone concentration on height at northern latitudes (yellow curve) and the level of blocking of solar ultraviolet by ozone. UVC is completely absorbed up to altitudes of 35 km. At the same time, UVA almost completely reaches the Earth's surface, but this radiation poses practically no danger. Ozone traps most of the UVB, but some reaches the Earth. In the event of depletion of the ozone layer, most of it will irradiate the surface and lead to genetic damage to living beings.
Brief list of uses of electromagnetic waves in the UV range.
- High quality photolithography for the manufacture of electronic devices such as microprocessors and memory chips.
- In the manufacture of fiber optic elements, in particular Bragg gratings.
- Disinfection from microbes of products, water, air, objects (UVC).
- Black light (UVA) in forensics, in the examination of works of art, in the establishment of the authenticity of banknotes (fluorescence phenomenon).
- Artificial tan.
- Laser engraving.
- Dermatology.
- Dentistry (photopolymerization of fillings).
man-made sources ultraviolet radiation are:
Non-monochromatic: Mercury discharge lamps of various pressures and designs.
Monochromatic:
- Laser diodes, mainly based on GaN, (low power), generating in the near ultraviolet range;
- Excimer lasers are very powerful sources of ultraviolet radiation. They emit nanosecond (picosecond and microsecond) pulses with an average power ranging from a few watts to hundreds of watts. Typical wavelengths lie between 157 nm (F2) to 351 nm (XeF);
- Some solid-state lasers doped with cerium, such as Ce3+:LiCAF or Ce3+:LiLuF4, which are pulsed with nanosecond pulses;
- Some fiber lasers, such as those doped with neodymium;
- Some dye lasers are capable of emitting ultraviolet light;
- Ion argon laser, which, despite the fact that the main lines lie in the optical range, can generate continuous radiation with wavelengths of 334 and 351 nm, but with lower power;
- Nitrogen laser emitting at a wavelength of 337 nm. A very simple and cheap laser, operates in a pulsed mode with a nanosecond pulse duration and with a peak power of several megawatts;
- Triple frequencies of Nd:YAG laser in nonlinear crystals;
Literature:
- Wikipedia "Ultraviolet".
Story
The first explanations of the causes of the visible radiation spectrum were given by Isaac Newton in the book Optics and Johann Goethe in 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. : Bolshaya 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 the uniformity of measurements. Light measurements. Values of the relative spectral luminous efficiency of monochromatic radiation for daytime vision
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 areas 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 color renders greater influence than red, with equal radiation power, and in the light - vice versa.
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 changing both the speed and wavelength, 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 man, 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.
> Visible light
Find out the definition and characteristics visible light: wavelength, electromagnetic radiation range, frequency, color spectrum diagram, color perception.
visible light
Visible light is the part of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range is simply called light. The eyes respond to visible light wavelengths of 390-750 nm. In terms of frequency, this corresponds to a band of 400-790 THz. An adapted eye typically achieves a maximum sensitivity of 555 nm (540 THz) in the green region of the optical spectrum. But the spectrum itself does not contain all the colors captured by the eyes and brain. For example, colorful ones such as pink and purple are created by combining several wavelengths.
Here are the main categories of electromagnetic waves. The dividing lines differ in some places, while other categories may overlap. Microwaves occupy the high-frequency section of the radio section of the electromagnetic spectrum
Visible light forms the vibrations and rotations of atoms and molecules, as well as the electronic transport within them. These transports are used by receivers and detectors.
A small part of the electromagnetic spectrum along with visible light. The separation between infrared, visible and ultraviolet is not 100% distinct
The top figure shows a part of the spectrum with colors that are responsible for specific pure wavelengths. Red is the lowest frequencies and longest wavelengths, while purple is the highest frequencies and shortest wavelengths. The solar black body radiation peaks in the visible part of the spectrum, but is more intense in the red than in the violet, which is why the star appears yellow to us.
The colors obtained by the light of a narrow band of wavelengths are called pure spectral. Don't forget that everyone has many shades because the spectrum is continuous. Any images that provide data from wavelengths are different from those that are present in the visible part of the spectrum.
Visible light and the earth's atmosphere
Visible light passes through the optical window. This is a "place" in the electromagnetic spectrum that allows waves to pass through without resistance. As an example, remember that the air layer scatters blue more than red, so the sky looks blue to us.
The optical window is also called the visible window because it covers the spectrum available to humans. This is no coincidence. Our ancestors developed a vision capable of using a huge variety of wavelengths.
Thanks to the presence of an optical window, we can enjoy relatively mild temperature conditions. The solar brightness function reaches its maximum in the visible range, which moves independently of the optical window. That is why the surface heats up.
Photosynthesis
Evolution has affected not only humans and animals, but also plants, which have learned to respond correctly to parts of the electromagnetic spectrum. Thus, vegetation transforms light energy into chemical energy. Photosynthesis uses gas and water to create oxygen. This is an essential process for all aerobic life on the planet.
This part of the spectrum is called the photosynthetically active region (400-700 nm), which overlaps with the range of human vision.