Traditional medicine

Who discovered the phenomenon of light dispersion. Which scientist discovered the phenomenon of dispersion

Sometimes, when the sun comes out again after a heavy downpour, you can see a rainbow. This happens because the air is saturated with tiny water dust. Each drop of water in the air acts as a tiny prism, splitting the light into different colors.

About 300 years ago, I. Newton passed the sun's rays through a prism. He discovered that white light is a “wonderful mixture of colors.”

This is interesting… Why are there only 7 colors in the spectrum of white light?

For example, Aristotle indicated only three colors of the rainbow: red, green, violet. Newton first identified five colors in the rainbow, and later ten. However, later he settled on seven colors. The choice is most likely explained by the fact that the number seven was considered “magical” (seven wonders of the world, seven weeks, etc.).

Light dispersion was first discovered experimentally by Newton in 1666, when passing a narrow beam of sunlight through a glass prism. In the spectrum of white light he obtained, he identified seven colors: From this experiment, Newton concluded that “light beams that differ in color differ in the degree of refraction.” Violet rays are refracted the most, red ones the least.

White light is a complex light made up of different wavelengths (frequencies). Each color has its own wavelength and frequency: red, orange, green, blue, indigo, violet - this decomposition of light is called a spectrum.

Waves of different colors are refracted differently in a prism: less red, more violet. The prism deflects waves of different colors at different angles. This behavior is explained by the fact that when light waves pass from air into a glass prism, the speed of the “red” waves changes less than that of the “violet”. Thus, the shorter the wavelength (the higher the frequency), the greater the refractive index of the medium for such waves.

Dispersion is the dependence of the refractive index of light on the vibration frequency (or wavelength).

For waves of different colors, the refractive indices of this substance different; As a result, when deflected by a prism, white light is decomposed into spectrum.

When a monochromatic light wave passes from air into matter, the wavelength of the light decreases, the oscillation frequency remains unchanged. The color remains unchanged.

When all the colors of the spectrum are superimposed, white light is formed.

Why do we see objects colored? Paint does not create color, it selectively absorbs or reflects light.

Basic summary:

Questions for self-control on the topic “Dispersion of Light”

What is light dispersion called?
Draw diagrams for obtaining the spectrum of white light using a glass prism.
Why does white light produce a spectrum when passing through a prism?
Compare the refractive indices for red and violet light.
Which light travels faster in a prism - red or violet?
How to explain the variety of colors in nature from the point of view of wave optics?
What color will surrounding objects be visible through a red filter? Why?

Lesson objectives:

Educational:
- introduce the concepts of spectrum, light dispersion;
- To acquaint students with the history of the discovery of this phenomenon.
- clearly demonstrate the process of decomposition of a narrow light beam into components of various color shades.
- identify the differences between these elements of the light beam.
- continue to form the scientific worldview of students.
Developmental:
- development of attention, imaginative and logical thinking, memory when studying this topic.
- stimulation cognitive motivation students.
- development of critical thinking.
Educational:
- nurturing interest in the subject;
- nurturing a sense of beauty, the beauty of the surrounding world.

Lesson type: a lesson in studying and initially consolidating new knowledge.

Teaching methods: conversation, story, explanation, experiment. (Information and development)

Requirements for basic level of training: be able to describe and explain the phenomenon of dispersion.

Equipment and materials: computer, color cards, plane-parallel plates

Lesson plan:

	Lesson steps	Time, min	Techniques and methods
1.	Color painting	5 min. (before class, during recess)	Choosing a color card that matches the mood for each student before class during recess.
2.	Motivation	2 min.	Teacher's story
3.	Organizational moment	3 min.	Reading a poem by a student
4.	Learning new material	19 min.	Teacher's story. Demonstration of experiments. Conversation on issues. Notes in notebooks.
5.	Consolidation Sinkwine	12 min.	Teacher consultation. Observation. Student answers. Compiling a syncwine
6.	Summing up. Color painting	3 min.	Summarizing the material studied. Each student selects a color card to match their mood at the end of the lesson.
7.	Homework	1 min.	Writing on the board. Teacher's comment.

Before the start of the lesson, during recess, conduct the “Class Color Design” diagnostic. Each student, entering the classroom, chooses a card with a certain color that matches his mood, and a “Class Color Chart” is drawn up at the beginning of the lesson.

Yellow color is good
Orange – very good
Red – joyful
Green – calm
Blue – sad
Brown – alarming
Black – bad
White – indifferent

Epigraph for the lesson:

Nature cannot be caught sloppy and half-naked; she is always beautiful.

R. Emerson (American philosopher of the 19th century)

PROGRESS OF THE LESSON

1. Motivation

Sunlight has always been and remains for a person a symbol of joy, eternal youth, all the good, the best that can be in life:

“Let there always be the Sun.
May there always be heaven..." -

Such words are in the famous song written by Lev Oshanin.
Even a physicist. Accustomed to dealing with facts, with accurate registration of phenomena, sometimes feels awkward when saying that light is electromagnetic waves of a certain wavelength and nothing more.
The wavelength of light is very short. Imagine the average sea wave, which would increase so much that it would occupy the entire Atlantic Ocean alone - from America to Lisbon in Europe. The wavelength of light at the same magnification would only slightly exceed the width of a book page.
Question:
– Where do these electromagnetic waves come from?
Answer:
– Their source is the Sun.
Together with visible radiation The sun sends us thermal radiation, infrared and ultraviolet. High temperature The sun is the main cause of the birth of these electromagnetic waves.

2. Organizational moment

Formulation of the topic and objectives of the lesson.

The topic of our lesson is “Dispersion of Light”. Today we need:

Introduce the concept of “spectrum”, “dispersion of light”;
Identify the features of this phenomenon - light dispersion;
Get acquainted with the history of the discovery of this phenomenon.

Activation of mental activity:

A student reads a poem

Scent of the Sun

The smell of the sun? What nonsense!
No, not nonsense.
Sounds and dreams in the sun,
Fragrances and flowers,
Everyone merged into a consonant chorus,
Everything is woven into one pattern.
The sun smells like herbs,
Fresh baths,
In the awakening spring
And resinous pine,
Delicately light woven
Drunk with lilies of the valley,
What bloomed victoriously
In the pungent smell of earth.
The sun shines with bells,
Green leaves
Breathes outside singing birds,
Breathe with the laughter of young faces.
So say to all the blind:
It will be for you!
You will not see the gates of heaven,
The sun has a scent
Sweetly intelligible only to us,
Visible to birds and flowers!
A. Balmont

3. Learning new material

A little history

Speaking about these ideas, we should start with Aristotle’s color theory (IV century BC). Aristotle argued that the difference in color is determined by the difference in the amount of darkness “mixed” with sunlight (white) light. Violet color, according to Aristotle, arises with the greatest addition of darkness to light, and red - with the least. Thus, the colors of the rainbow are complex colors, and the main one is white light. It is interesting that the appearance of glass prisms and the first experiments in observing the decomposition of light by prisms did not give rise to doubts about the correctness of Aristotle’s theory of the appearance of colors. Both Hariot and Marzi remained followers of this theory. This should not be surprising, since at first glance the decomposition of light by a prism into various colors seemed to confirm the idea that color arises as a result of the mixing of light and darkness. The rainbow stripe appears precisely at the transition from the shadow stripe to the illuminated stripe, that is, at the border of darkness and white light. From the fact that the violet ray travels the longest path inside the prism compared to other colored rays, it is not surprising to conclude that the violet color occurs when white light loses its “whiteness” the most when passing through the prism. In other words, on the longest path, the greatest mixing of darkness to white light occurs. It was not difficult to prove the falsity of such conclusions by performing corresponding experiments with the same prisms. However, no one had done this before Newton.

Sunlight has many secrets. One of them is dispersion phenomenon. The great English physicist was the first to discover it Isaac Newton in 1666 while improving the telescope.

Light dispersion(decomposition of light) is a phenomenon caused by the dependence of the absolute refractive index of a substance on the frequency (or wavelength) of light (frequency dispersion), or, the same thing, the dependence of the phase speed of light in a substance on the wavelength (or frequency).

The dispersion of light was discovered experimentally by I. Newton around 1672, although theoretically it was quite well explained much later.
One of the most illustrative examples dispersion - the decomposition of white light when passing through a prism (Newton's experiment). The essence of the dispersion phenomenon is the unequal speed of propagation of light rays with different wavelengths in a transparent substance - an optical medium (while in a vacuum the speed of light is always the same, regardless of the wavelength and therefore color). Typically, the higher the frequency of the wave, the higher the refractive index of the medium and the lower its speed of light in it:

in red maximum speed in the medium and the minimum degree of refraction,
The violet color has the minimum speed of light in the medium and the maximum degree of refraction.

Light dispersion made it possible for the first time to demonstrate quite convincingly the composite nature of white light.

White light is decomposed into a spectrum and, as a result of passing through diffraction grating or reflection from it (this is not related to the phenomenon of dispersion, but is explained by the nature of diffraction).

The diffraction and prismatic spectra are somewhat different: the prismatic spectrum is compressed in the red part and stretched in the violet, and is arranged in descending order of wavelength: from red to violet; normal (diffraction) spectrum is uniform in all areas and is arranged in order of increasing wavelengths: from violet to red.

Knowing that white light has a complex structure, we can explain the amazing variety of colors in nature. If an object, such as a sheet of paper, reflects all the rays of different colors falling on it, then it will appear white. By covering the paper with a layer of red paint, we do not create a new color of light, but retain some of the existing light on the sheet. Now only red rays will be reflected, the rest will be absorbed by the paint layer. Grass and tree leaves seem green to us because of all the leaves that fall on them sun rays they reflect only green ones, absorbing the rest. If you look at the grass through red glass, which transmits only red rays, it will appear almost black.

The phenomenon of dispersion, discovered by Newton, is the first step towards understanding the nature of color. The depth of understanding of dispersion came after the dependence of color on the frequency (or wavelength) of light was clarified.

Thomas Young (1773-1829) was the first to measure wavelengths in 1802 different colors.

After the discovery of light dispersion, the wavelength became the main quantity determining the color of light. The main color receptor is the retina of the eye.

Color- there is a feeling that arises in retina eyes when it is excited by a light wave of a certain length. Knowing the wavelength of the emitted light and the conditions of its propagation, it is possible to predict in advance with a high degree of accuracy what color the eye will see.

It may be that the retina of the eye perceives one of the primary colors poorly or does not react to it at all, then this person’s color perception is impaired. This type of vision deficiency is called color blindness.

Good color perception is very important for a number of professions: sailors, pilots, railway workers, surgeons, artists. Special devices have been created - anomaloscopes for the study of color vision disorders.

Dispersion explains the fact that a rainbow appears after rain (more precisely, the fact that the rainbow is multi-colored and not white).
First attempt to explain rainbow as a natural phenomenon was made in 1611 by Archbishop Antonio Dominis.

1637 – scientific explanation Rainbows were first given by Rene Descartes. He explained the rainbow based on the laws of refraction and reflection of sunlight in raindrops. The phenomenon of dispersion had not yet been discovered, which is why Descartes' rainbow turned out to be white.

30 years later Isaac Newton complemented Descartes' theory and explained how colored rays are refracted in raindrops.

“Descartes hung the rainbow in the right place in the sky, and Newton colored it with all the colors of the spectrum.”

American scientist A. Fraser

Rainbow is an optical phenomenon associated with the refraction of light rays by numerous raindrops. However, not everyone knows exactly how the refraction of light on raindrops leads to the appearance of a giant multicolored arc in the sky. Therefore, it is useful to dwell in more detail on the physical explanation of this spectacular optical phenomenon.

Rainbow through the eyes of an attentive observer. First of all, a rainbow can only be observed in the direction opposite to the Sun. If you stand facing the rainbow, the Sun will be behind you. A rainbow occurs when the Sun illuminates a curtain of rain. As the rain subsides and then stops, the rainbow fades and gradually disappears. The colors observed in a rainbow alternate in the same sequence as in the spectrum obtained by passing a beam of sunlight through a prism. In this case, the inner (facing the Earth’s surface) extreme region of the rainbow is colored purple, and the outermost region is in red. Often, another (secondary) rainbow appears above the main rainbow - wider and blurrier. The colors in the secondary rainbow alternate in the reverse order: from red (the innermost region of the arc) to violet (the outermost region).

For an observer standing on relatively flat earth's surface, a rainbow appears provided that the angular height of the Sun above the horizon does not exceed approximately 42°. The lower the Sun, the greater the angular height of the top of the rainbow and, therefore, the larger the observed portion of the rainbow. A secondary rainbow can be observed if the height of the Sun above the horizon does not exceed approximately 52.

The rainbow can be considered as a giant wheel, which, like an axle, is mounted on an imaginary straight line passing through the Sun and the observer.

Dispersion is the cause of chromatic aberrations - one of the aberrations of optical systems, including photographic and video lenses.

Dispersion of light in nature and art

Due to dispersion, different colors of light can be observed.
The rainbow, whose colors are due to dispersion, is one of the key images of culture and art.
Thanks to light dispersion, it is possible to observe the colored “play of light” on the facets of a diamond and other transparent faceted objects or materials.
To one degree or another, rainbow effects are found quite often when light passes through almost any transparent object. In art they can be specifically intensified and emphasized.
The decomposition of light into a spectrum (due to dispersion) when refracted in a prism is a fairly common topic in the visual arts. For example, the cover of the album Dark Side Of The Moon by Pink Floyd depicts the refraction of light in a prism with decomposition into a spectrum.

The discovery of dispersion was very significant in the history of science. On the scientist’s tombstone there is an inscription with the following words: “Here lies Sir Isaac Newton, the nobleman who ... was the first with the torch of mathematics to explain the movements of the planets, the paths of comets and the tides of the oceans.

He investigated the difference in light rays and the various properties of colors that manifest themselves, which no one had previously suspected. …Let mortals rejoice that such an adornment of the human race existed.”

4. Consolidation

Answer questions on the topic studied.
Category "Think..."
Question: Why is a rainbow round?
Compilation of “Sinquain” on the topic “Variance”

5. Summing up the lesson

At the end of the lesson, conduct the “Class Coloring” diagnostic again. Find out what the mood was at the end of the lesson, on the basis of which a “Class Color Design” diagram is drawn up and the result is compared, what mood the students were in at the beginning of the lesson and at the end.

6. Homework:§66

Literature:

Myakishev G.Ya., Bukhovtsev B.B. Physics: Textbook for 11th grade high school. – M.: Education, 2006.
Rymkevich A.P. Collection of problems in physics for grades 9-11 of high school. – M.: Education, 2006.
Reader on physics: Tutorial for students in grades 8-10 of secondary school / Ed. B.I. Spassky. – M.: Education, 1987.
Journal "Physics at School" No. 1/1998

Every hunter wants to know where the pheasant is sitting. As we remember, this phrase means the sequence of colors of the spectrum: red, orange, yellow, green, blue, indigo and violet. Who showed that white this is the totality of all colors, what does a rainbow, beautiful sunsets and sunrises, shine have to do with this precious stones? All these questions are answered by our lesson, the topic of which is: “Dispersion of Light.”

Until the second half of the 17th century, it was not completely clear what color was. Some scientists said that this is a property of the body itself, some stated that these are different combinations of light and dark, thereby confusing the concepts of color and illumination. Such color chaos reigned until Isaac Newton conducted an experiment on transmitting light through a prism (Fig. 1).

Rice. 1. Path of rays in a prism ()

Let us remember that a ray passing through a prism undergoes refraction when passing from air to glass and then another refraction - from glass to air. The trajectory of the ray is described by the law of refraction, and the degree of deviation is characterized by the refractive index. Formulas describing these phenomena:

Rice. 2. Newton's experiment ()

In a dark room, a narrow beam of sunlight penetrates through the shutters; Newton placed a glass triangular prism in its path. A beam of light passing through a prism was refracted in it, and a multi-colored strip appeared on the screen behind the prism, which Newton called a spectrum (from the Latin “spectrum” - “vision”). White color turned into all colors at once (Fig. 2). What conclusions did Newton make?

1. Light has a complex structure (speaking modern language- white light contains electromagnetic waves of different frequencies).

2. Light of different colors differs in the degree of refraction (characterized by different indicators refraction in a given medium).

3. The speed of light depends on the medium.

Newton outlined these conclusions in his famous treatise “Optics”. What is the reason for this decomposition of light into a spectrum?

As Newton's experiment showed, red was the weakest refracted color, and violet was the most refracted. Recall that the degree of refraction of light rays is characterized by the refractive index n. Red color differs from violet in frequency; red has a lower frequency than violet. Since the refractive index increases as we move from the red end of the spectrum to the violet end, we can conclude that the refractive index of glass increases as the frequency of light increases. This is the essence of the phenomenon of dispersion.

Let's remember how the refractive index is related to the speed of light:

n ~ ν; V ~ => ν =

n - refractive index

C - speed of light in vacuum

V - speed of light in the medium

ν - frequency of light

This means that the higher the frequency of light, the lower the speed of light propagating in glass, thus, the highest speed inside a glass prism is red, and the lowest speed is violet.

The difference in the speeds of light for different colors occurs only in the presence of a medium; naturally, in a vacuum, any ray of light of any color propagates at the same speed m/s. Thus, we found out that the reason for the decomposition of white color into a spectrum is the phenomenon of dispersion.

Dispersion- dependence of the speed of light propagation in a medium on its frequency.

The phenomenon of dispersion, discovered and studied by Newton, awaited its explanation for more than 200 years; only in the 19th century, the Dutch scientist Lawrence proposed classical theory variances.

The reason for this phenomenon is the interaction of external electromagnetic radiation, that is, light with the medium: the higher the frequency of this radiation, the more stronger interaction, which means the more the beam will deviate.

The dispersion that we talked about is called normal, that is, the frequency indicator increases if the frequency of electromagnetic radiation increases.

In some rare media, anomalous dispersion is possible, that is, the refractive index of the medium increases as the frequency decreases.

We saw that each color corresponds to a specific wavelength and frequency. Wave corresponding to the same color in different environments has the same frequency but different wavelengths. Most often, when talking about the wavelength corresponding to a certain color, they mean the wavelength in vacuum or air. The light corresponding to each color is monochromatic. “Mono” means one, “chromos” means color.

Rice. 3. Arrangement of colors in the spectrum according to wavelengths in the air ()

The longest wavelength is red (wavelength - from 620 to 760 nm), the shortest wavelength is violet (from 380 to 450 nm) and the corresponding frequencies (Fig. 3). As you can see, there is no white color in the table, white color is the sum of all colors, this color does not correspond to any strictly defined wavelength.

What explains the colors of the bodies that surround us? They are explained by the body’s ability to reflect, that is, scatter radiation incident on it. For example, a white color, which is the sum of all colors, falls on some body, but this body best reflects the red color, and absorbs other colors, then it will seem exactly red to us. The body that best reflects blue will appear blue and so on. If the body reflects all colors, it will end up appearing white.

It is the dispersion of light, that is, the dependence of the refractive index on the wave frequency, that explains the beautiful phenomenon of nature - the rainbow (Fig. 4).

Rice. 4. The phenomenon of the rainbow ()

Rainbows occur because sunlight refracted and reflected by droplets of water, rain or fog floating in the atmosphere. These droplets deflect light of different colors in different ways, as a result, white color is decomposed into a spectrum, that is, dispersion occurs; an observer who stands with his back to the light source sees a multi-colored glow that emanates from space along concentric arcs.

Dispersion also explains the remarkable play of color on the facets of precious stones.

1. The phenomenon of dispersion is the decomposition of light into a spectrum, due to the dependence of the refractive index on the frequency of electromagnetic radiation, that is, the frequency of light. 2. Body color is determined by the body’s ability to reflect or scatter a particular frequency of electromagnetic radiation.

References

Tikhomirova S.A., Yavorsky B.M. Physics (basic level) - M.: Mnemosyne, 2012.
Gendenshtein L.E., Dick Yu.I. Physics 10th grade. - M.: Mnemosyne, 2014.
Kikoin I.K., Kikoin A.K. Physics - 9, Moscow, Education, 1990.

Homework

What conclusions did Newton draw after his experiment with a prism?
Define dispersion.
What determines body color?

Internet portal B -i-o-n.ru ().
Internet portal Sfiz.ru ().
Internet portal Femto.com.ua ().

) light (frequency dispersion), or, the same thing, the dependence of the phase speed of light in a substance on frequency (or wavelength). Experimentally discovered by Newton around 1672, although theoretically quite well explained much later.

Spatial dispersion is the dependence of the dielectric constant tensor of a medium on the wave vector. This dependence causes a number of phenomena called spatial polarization effects.

Encyclopedic YouTube

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Dispersion and spectrum of light

Light Dispersion and Body Color

Dispersion of light. Body colors

Subtitles

Properties and manifestations

One of the most obvious examples of dispersion is the decomposition of white light as it passes through a prism (Newton's experiment). The essence of the dispersion phenomenon is the difference in the phase speeds of propagation of light rays of different wavelengths in a transparent substance - an optical medium (while in a vacuum the speed of light is always the same, regardless of the wavelength and therefore color). Typically, the shorter the wavelength of light, the greater the refractive index of the medium for it and the less phase speed waves in the medium:

red light has a maximum phase speed of propagation in the medium and a minimum degree of refraction,
For violet light, the phase speed of propagation in the medium is minimal, and the degree of refraction is maximum.

However, in some substances (for example, iodine vapor), an anomalous dispersion effect is observed, in which blue rays are refracted less than red ones, while other rays are absorbed by the substance and elude observation. More strictly speaking, anomalous dispersion is widespread, for example, it is observed in almost all gases at frequencies near absorption lines, but in iodine vapor it is quite convenient for observation in the optical range, where they absorb light very strongly.

Light dispersion made it possible for the first time to demonstrate quite convincingly the composite nature of white light.

Augustin Cauchy proposed an empirical formula for approximating the dependence of the refractive index of a medium on wavelength:

n = a + b / λ 2 + c / λ 4 (\displaystyle n=a+b/\lambda ^(2)+c/\lambda ^(4)),

Where λ (\displaystyle \lambda)- wavelength in vacuum; a, b, c- constants, the values of which for each material must be determined experimentally. In most cases, you can limit yourself to the first two terms of the Cauchy formula. Subsequently, other more accurate, but at the same time more complex, approximation formulas were proposed.

The world around us is filled with millions of different shades. Thanks to the properties of light, every object and object around us has a certain color perceived by human vision. The study of light waves and their characteristics has allowed people to take a deeper look at the nature of light and the phenomena associated with it. Today we'll talk about variance.

Nature of light

From a physical point of view, light is a combination electromagnetic waves With different meanings length and frequency. The human eye does not perceive any light, but only that whose wavelength ranges from 380 to 760 nm. The remaining varieties remain invisible to us. These include, for example, infrared and ultraviolet radiation. The famous scientist Isaac Newton imagined light as a directed stream of the most fine particles. It was only later that it was proven that it is a wave in nature. However, Newton was still partly right. The fact is that light has not only wave, but also corpuscular properties. This is confirmed by the well-known phenomenon of the photoelectric effect. It turns out that the luminous flux has a dual nature.

Color spectrum

White light, accessible to human vision, is a combination of several waves, each of which is characterized by a certain frequency and its own energy of photons. Accordingly, it can be decomposed into waves different colors. Each of them is called monochromatic, and a certain color corresponds to its own range of length, wave frequency and photon energy. In other words, the energy emitted by a substance (or absorbed) is distributed according to the above indicators. This explains the existence of the light spectrum. For example, the green color of the spectrum corresponds to frequencies ranging from 530 to 600 THz, and violet from 680 to 790 THz.

Each of us has ever seen how rays shimmer on cut glass products or, for example, on diamonds. This can be observed due to a phenomenon called light dispersion. This is an effect that reflects the dependence of the refractive index of an object (substance, medium) on the length (frequency) of the light wave that passes through this object. The consequence of this dependence is the decomposition of the beam into a color spectrum, for example, when passing through a prism. Light dispersion is expressed by the following equality:

where n is the refractive index, ƛ is the frequency, and ƒ is the wavelength. The refractive index increases with increasing frequency and decreasing wavelength. We often observe dispersion in nature. Its most beautiful manifestation is the rainbow, which is formed due to the scattering of sunlight as it passes through numerous raindrops.

The first steps towards the discovery of variance

As mentioned above, the luminous flux, when passing through a prism, is decomposed into a color spectrum, which Isaac Newton studied in sufficient detail in his time. The result of his research was the discovery of the phenomenon of dispersion in 1672. Scientific interest to the properties of light appeared even before our era. The famous Aristotle already noticed that sunlight can have different shades. The scientist argued that the nature of color depends on the "amount of darkness" present in white light. If there is a lot of it, then a purple color appears, and if there is little, then red. Great thinker also said that the main color of light rays is white.

Studies of Newton's predecessors

Aristotle's theory of the interaction of darkness and light was not refuted by scientists of the 16th and 17th centuries. Both the Czech researcher Marzi and the English physicist Hariot independently conducted experiments with a prism and were firmly convinced that the reason for the appearance of different shades of the spectrum was precisely the mixing of the light flux with darkness when passing through the prism. At first glance, the scientists' conclusions could be called logical. But their experiments were rather superficial and they were unable to back them up additional research. That was until Isaac Newton got down to business.

Newton's discovery

Thanks to the inquisitive mind of this outstanding scientist, it was proven that white light is not the main one, and that other colors do not arise as a result of the interaction of light and darkness in different proportions. Newton refuted these beliefs and showed that white light is composite in its structure, it is formed by all the colors of the light spectrum, called monochromatic. As a result of the passage of a light beam through a prism, a variety of colors are formed due to the decomposition of white light into its constituent wave streams. Such waves with different frequencies and length refract differently in the medium, forming a certain color. Newton performed experiments that are still used in physics today. For example, experiments with crossed prisms, using two prisms and a mirror, and passing light through prisms and a perforated screen. Now we know that the decomposition of light into a color spectrum occurs due to different speeds of passage of waves with different lengths and frequency through transparent matter. As a result, some waves leave the prism earlier, others a little later, others even later, and so on. This is how the light flux decomposes.

Anomalous dispersion

Subsequently, physicists of the century before last made another discovery regarding dispersion. The Frenchman Leroux discovered that in some media (in particular, in iodine vapor), the dependence expressing the phenomenon of dispersion is violated. The physicist Kundt, who lived in Germany, took up the study of this issue. For his research, he borrowed one of Newton's methods, namely an experiment using two crossed prisms. The only difference was that instead of one of them, Kundt used a prismatic vessel with a cyanine solution. It turned out that the refractive index when light passes through such prisms increases, and does not decrease, as happened in Newton's experiments with ordinary prisms. The German scientist found that this paradox is observed due to a phenomenon such as the absorption of light by matter. In the described Kundt experiment, the absorbing medium was a cyanine solution, and the dispersion of light for such cases was called anomalous. IN modern physics this term is practically not used. To date, the normal one discovered by Newton and discovered later anomalous dispersion are considered as two phenomena related to one doctrine and having a common nature.

Low dispersion lenses

In photographic technology, light dispersion is considered undesirable phenomenon. It causes so-called chromatic aberration, in which colors appear distorted in images. The shades of the photograph do not match the shades of the subject being photographed. This effect becomes especially unpleasant for professional photographers. Due to dispersion in photographs, not only colors are distorted, but edges are often blurred or, conversely, an overly defined border appears. Global photographic equipment manufacturers are coping with the consequences of this optical phenomenon using specially designed low dispersion lenses. The glass from which they are made has the excellent property of refracting waves of different lengths and frequencies equally. Lenses in which low-dispersion lenses are installed are called achromats.