Physics presentation on the topic "Dispersion of light" free download. Physics presentation on the topic "Dispersion of light" free download Refraction of light dispersion of colors of bodies presentation
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Presentation - Light dispersion
The text of this presentation
Physics lesson in 11 (8) class
Light dispersion
ANNOTATION:
The presentation allows you to conduct a lesson on the topic: "Dispersion of light" The presentation is designed to enhance the cognitive activity of students. development of thinking, initiative in acquiring knowledge, development of interest in the study of physics. Computer support of the lesson can be used to enrich its content. Used ITC: working with text, drawings, searching for illustrative material on the Internet, scanning. The presentation consists of 20 slides, the amount of memory is 2.11KB
Goals:
1 To get acquainted with the concept of light dispersion, to study the wave properties of light; 2 Explain the rainbow phenomenon based on physical concepts; 3 Find out what color is.
Epigraph
How unexpectedly and brightly On the wet blue sky, an airy arch was erected In its momentary triumph! She plunged one end into the forests, She left behind the clouds with the other, She embraced half the sky And fainted in the height. F.I. Tyutchev
Introduction to the phenomenon
300 years ago, the English physicist Isaac Newton, studying the phenomenon of refraction of light passing through a glass prism, discovered an amazing phenomenon. A beam of sunlight, falling on a prism, is refracted, and a multi-colored strip of light appears on the opposite wall, which is called the SPECTRUM. Thus, white light is a "wonderful mixture of colors."
7 COLORS OF THE DISPERSION SPECTRUM:
1 RED 2 ORANGE 3 YELLOW 4 GREEN 5 BLUE 6 BLUE 7 PURPLE
Spectrum colors
This is interesting …
Why are there only 7 colors in the white light spectrum? Aristotle, for example, indicated only three colors: red, green, purple. Newton first identified five colors, and later ten. However, he later settled on seven colors. The choice is explained, most likely, by the fact that the number "seven" was considered magical (seven wonders of the world, seven days of the week, etc.)
Physical dictionary
Spectrum - from the Latin word spectrum - visible, vision. Dispersion - from the Latin word dispersus - scattered, scattered. Chromatism is from the Greek word for color. Inversion - from the Latin word inversio - turning over, moving.
DEFINITION Dispersion of light - the dependence of the refractive index of a substance on the wavelength (frequency) of light. The phenomenon was discovered by Isaac Newton (1643-1727) in 1666
In glass, the speed of the violet wave is less than the speed of the red, and therefore it, passing through the prism, is refracted more strongly.
RAINBOW
Sometimes, when the sun comes out again after a heavy downpour, you can see a rainbow. This is because the air is saturated with fine water dust. Each drop of water in the air plays the role of a tiny prism, crushing the light into different colors.
Rainbow is a special case of CAUSTIC, the play of light. To see it, you need to stand with your back to the sun after the rain. A multi-colored arc is usually located at a distance of 1-2 km from the observer, and sometimes it can be observed at a distance of 2-3 m against the background of water drops formed by fountains or water sprays.
The center of the rainbow is on the continuation of the straight line connecting the Sun and the eye of the observer - on the counter-solar line. The angle between the direction to the main rainbow and the antisolar line is 41-42 degrees.
How is a rainbow formed?
A rainbow appears as a result of reflection of light from the inner surface of a raindrop and double refraction - when entering and leaving the drop. The rainbow theory was first given in 1637 by René Descartes.
The shape of the arc, the brightness of the colors, the width of the stripes depend on the size of the water droplets and their number. Large drops create a narrower rainbow, with sharply prominent colors, small drops create an arc that is blurry, faded and even white. That is why a bright narrow rainbow is visible in the summer after a thunderstorm, during which large drops fall.
Why do we sometimes see a second rainbow?
The reason for the second rainbow, like the first, is the refraction and reflection of light in water droplets. However, before turning into a “second rainbow”, the rays of sunlight have time to reflect twice, and not once, from the inner surface of each droplet.
Please note that the sequence of colors in the "second rainbow" is REVERSE to that seen in the "primary". The brightness of the "second rainbow" is less than the first due to the fact that both internal reflections are not complete and part of the light comes out of the drop.
Why is the rainbow round?
The fact is that each raindrop has an approximately spherical shape, and the parallel beam of sunlight falling on it turns into a multi-colored circle as a result of refraction and internal reflection.
In the eye of the observer, as in the top of a circular cone with an angle at the top of 42 degrees, rays are collected, diverging from many droplets and forming a circle of the same angular size. If the "eye" moves, the whole rainbow picture moves - in each specific place it forms its own set of droplets.
Light dispersion
The psychological impact of light.
Psychological research in the middle of the twentieth century. showed that each color has a very specific psychophysical effect, independent of the individual characteristics of a person. Differences occur at the level of the psychological reaction of each person to a particular color. Red. Contributes to the treatment of all viral diseases., Stimulates the immune system. Strengthens memory, invigorates energy throughout the body, increases muscle strength. Orange. Increases the level of neuroendocrine regulation, has a rejuvenating effect on the entire body. Yellow. Produces a cleansing effect on the entire body. Stimulates appetite. This is a physiologically optimal color, it tones the nervous system, stimulates vision.
The psychological impact of light. (continued)
Green. Normalizes cardiac activity, calms the central nervous system. This is the color of relaxation, relieving nervous tension. Blue. Contributes to the normalization of blood pressure, cardiac activity. It is used in the treatment of diseases of the eyes and liver. Blue. It has an unusually beneficial effect on the entire endocrine system. Treats diseases of the lungs and eyes. Violet. It has a calming effect on the nervous system. It has a positive effect on the vascular system.
GAME "Find your color"
RED 1 A AND C ORANGE 2 BY T Y YELLOW 3 B G GREEN 4 GL V CYAN 5 D M HYU BLUE 6 EN C Y PURPLE 7 Y O B PINK 8 Y R W GOLD 9 Z R Щ Write your name (last name, nickname, abbreviation, etc.), fill in the appropriate numbers and sum them up. If the result is a number greater than 10, add up its digits and continue with the resulting numbers until the sum is less than 10. Similarly, to determine the color of the date of birth, sum the digits of its constituent numbers. TRY TO MATCH YOUR BOTH COLORS.
PROVERBS, SAYINGS, RIDDLES
High and steep rainbow - to the bucket, flat and low - to bad weather. Rainbow - arc, interrupt the rain. The bridge stretched for seven villages, for seven miles. Shirt outside, sleeves in the hut. A painted yoke hung across the river. A red cloth stretches through the window. You look - you cry, but there is no more beautiful than him in the world. Find proverbs and sayings related to the studied phenomena.
Answer the questions:
1 Why is white light able to decompose into a spectrum when passing through a glass prism? 2 Who discovered the phenomenon of dispersion? 3 What is dispersion? 4 How to explain the variety of colors visible to man in nature? 5 How do different colors differ from each other? 6 What is a rainbow? Why do we see the sky blue and the dawn red?
Consequences
White light is a set of waves of different frequencies.
A substance selectively absorbs light waves of different frequencies.
Getting into the human eye, light waves of different frequencies have a different effect on the retina.
Each color has its own wave frequency.
"FRAGRANCE OF THE SUN" The smell of the sun? What nonsense! No, not nonsense.
In the sun, sounds and dreams, Aromas and flowers, All merged into a consonant choir, All intertwined into one pattern. The sun smells of herbs, Fresh kupava, Awakened in the spring And resinous pine, Gently - light-woven, Drunk lilies, That triumphantly blossomed In the pungent smell of the earth.
The sun shines with ringing, Green leaves, Breathes the spring song of birds, Breathes the laughter of young faces. So say to all the blind: It will be for you! You will not behold the gates of paradise, The sun has a fragrance, Sweetly intelligible only to us, Visible to birds and flowers! K. Balmont
Literature:
1 “The first of September. Physics”, No. 33/03; 11/04; 3/06; 6/06; 2 S.V. Zvereva "In the world of sunlight"; L.: Gidrometeoizdat, 1988 3 V.L. Bulat "Optical phenomena in nature"; M.; Enlightenment, 1985 4 G. Ya. Myakishev, B. B. Bukhovtsev "Physics. Grade 11", M .; Education, 2006-2007 5 A.I. Semke "Physics. Entertaining materials for lessons "; M.; NTs ENAS, 2006
A zebra and a rainbow are somewhat similar: A zebra is striped, a rainbow too. Let life be a striped zebra, But not two-color, but multi-colored! life illuminates with love. Blue - will raise you above the vanity. It will be a bright and good dream! I wish you such colors, great happiness and longevity!
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Dispersion - sounds great word; Beautiful and the phenomenon itself It is close and familiar to us from childhood, We have observed it hundreds of times! The thunder has died down, the summer downpour has died down quickly; And a rainbow hung over the freshly washed earth With a disembodied bridge, Captivating us with its beauty. Dispersion here "had a hand in it." The usual white ray of light She, as if spread out in a prism, In the raindrop he met.
Outstanding English physicist and mathematician, founder of classical mechanics. I. Newton was born into the family of a poor farmer in the town of Woolsthorpe, near the town of Grantham. At the age of 12, he began studying at Grantham School. In 1661, Newton entered one of the colleges of the University of Cambridge and after graduation he received a bachelor's degree. An exceptional role in Newton's life was played by 1665 - 1667, which he spent in his native Woolsthorpe, hiding from the plague. Here he basically developed those ideas that led the scientist to important discoveries: the creation of the mathematical basis of physics - differential and integral calculus, the discovery of the law of universal gravitation, the invention of a mirror telescope; here he conducted experiments on the decomposition of light. In 1668, Newton was awarded a master's degree, and then he headed the physical and mathematical department at the University of Cambridge. In 1672 He was elected a member of the Royal Society of London, and in 1703. Became its president.
Newton's experiments Newton sent a white beam to a glass prism. As soon as visible light enters the prism, it is refracted and decomposed into an iridescent strip, which is called the spectrum. White color is conventionally divided into seven colors. As experience has shown, each color has its own refractive index: the largest is violet, the smallest is red. As we already know from light diffraction experiments, colors have different wavelengths. Light passing through a trihedral prism is refracted and, upon exiting the prism, deviates from its original direction towards the base of the prism. The magnitude of the deflection of the beam depends on the refractive index of the substance of the prism, and, as experiments show, the refractive index depends on the frequency of the light.
The considered experiments were first made in 1666 by the English physicist Isaac Newton. The figure shows one of the experiments set by Newton himself. Newton in his experiments used sunlight, which he passed into the room through a narrow hole in the window shutter.
Each color corresponds to its own wavelength and frequency, such a single-color light is called - monochromatic Color Wavelength, nm Section width, nm Red Orange Yellow585 - Green Blue510 - Blue480 - Violet
CONCLUSIONS FROM NEWTON'S EXPERIMENTS White light is not monochromatic. The second prism only refracts the rays, but does not change their color. These rays were called simple or monochromatic. White light consists of monochromatic - simple colors. The refractive index of a medium depends on the color of the light: rays of red light in any medium are refracted more weakly than all others. When leaving the prism, white light is decomposed into seven colors: red, orange, yellow, green, blue, indigo, violet. The red light is deflected the least, the violet the most. Light with different wavelengths propagates in a medium with different speeds: violet at the lowest, red at the highest, since n = c/v.
COLORS OF OPAQUE BODIES The variety of colors and shades in the world around us explains the phenomenon of dispersion. When interacting with different bodies, rays of light of different colors are reflected and absorbed by these bodies in different ways. Bodies painted white reflect rays of light of different frequencies equally well. Bodies painted black absorb light rays of different frequencies equally well. Opaque bodies are painted in the color whose rays of light they reflect well. With the help of light dispersion, such a phenomenon as a rainbow can be explained.
COLORS OF TRANSPARENT BODIES COLORS OF TRANSPARENT BODIES The color of a transparent body is determined by the composition of the light that passes through it. If a transparent body uniformly absorbs the rays of all colors, then in transmitted white light it is colorless, and in colored light it has the color of those rays with which it is illuminated. When white light is passed through tinted glass, it lets through the color it is painted with. This property is used in various light filters.
GENERALIZATION OF THE MATERIAL Dispersion of light is the phenomenon of decomposition of white light into a spectrum with the help of a prism. The order of the colors in the spectrum does not change. The dispersion of light occurs because the refractive index of the medium depends on the color of the light. The dispersion of light proves that white light is complex, consisting of simple - monochromatic colors. The dispersion makes it possible to explain the colors of opaque bodies by the fact that the bodies reflect and absorb light of different frequencies in different ways.
Consolidation. 1. Observe the formation of colored circles around the street lamp bulb and explain this phenomenon, note the sequence of circles. (The explanation should be related to the refractive index of colored rays with the propagation velocity Vcr.> Vf) 2. Why do we see white - white, black - black, red - red? 3. Observe a white sheet of paper through colored glass and explain why the paper takes on the color of glass? Vph) 2. Why do we see white - white, black - black, red - red? 3. Observe a white sheet of paper through colored glass and explain why the paper takes on the color of glass?"> 
4. “Excellent” and green “good” are written on the notebook in red pencil. There are two glasses, red and green, which one should be looked through to see the “excellent” rating? 5. On the gray background of the stage is a figure in red. What kind of light should be illuminated to create the appearance of disappearance? 6. From Jules Verne's story "The Green Beam": "Have you ever seen the setting sun on the horizon? - Yes, sure! “… But have you noticed how the last ray of sunshine appears and goes out when the air is freed from fog and becomes transparent? – Probably not! And so, if you imagine seeing this phenomenon - it happens very rarely - then pay attention to the fact that this last ray will not be red, but green. Yes, yes, it will have a wonderful green color, that is, such a green that no artist can create on his palette. Such a green color cannot be found anywhere in nature, because it cannot be found in the plant world, despite all the multitude and diversity, even near the brightest seas.
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Slides captions:
dispersion of light.
Newton's experiment on the dispersion of light Newton directed a light beam of small cross section onto a prism. A beam of sunlight entered the darkened room through a small hole in the shutter.
Falling on a glass prism, the light beam was refracted and gave an image with iridescent alternation of colors on the opposite wall. Newton identified seven colors: Violet Blue Blue Green Yellow Orange Red He called the rainbow stripe spectrum. Newton's experiment on the dispersion of light
The color depends on the physical characteristics of the light wave: the frequency of oscillation or the wavelength. Red light has the longest wavelength and violet light the shortest. Newton's experiment on the dispersion of light
The dependence of the refractive index of light on the oscillation frequency (or wavelength) is called dispersion. Newton made an important conclusion: "Light beams that differ in color differ in the degree of refraction." Newton's experiment on the dispersion of light
The refractive index is determined by the formula: n=c/ υ where c = 300,000 km/s is the speed of light in vacuum u is the speed of a set in a medium If light of different colors is refracted differently, then the speed of monochromatic waves in a substance is different. The refractive index for red light in glass is 1.64 and for violet 1.68. Dispersion and refractive index
Spectroscope and spectrograph O – eyepiece ST – spotting scope P – prism K – collimator Shch – sliding slit
Spectral analysis Emission spectra: 1 – continuous; 2 - sodium; 3 - hydrogen; 4 - helium. Absorption spectra: 5 - solar; 6 - sodium; 7 - hydrogen; 8 - helium.
Links to illustrations: http://im6-tub-ru.yandex.net/i?id=67146028-45-72. http://im4-tub-ru.yandex.net/i?id=46045339-28-72 . http://im4-tub-ru.yandex.net/i?id=289692535-28-72 . http://im5-tub-ru.yandex.net/i?id=344390577-21-72 . http://im7-tub-ru.yandex.net/i?id=496547705-61-72 . http://de.trinixy.ru/pics4/20110525/podb/12/amazing_nature_pics_17.jpg ; http://yro.narod.ru/bibliotheca/Icons/Ikoni/raduga.jpg ; http://www.eaas.co.uk/images/atmospheric_optics/rainbow.jpg ; http://im2-tub-ru.yandex.net/i?id=945671994-10-72 ; http://www.olympusmicro.com/primer/images/diffraction/rainbow.jpg . http://im8-tub-ru.yandex.net/i?id=139297492-17-72 ; http://im4-tub-ru.yandex.net/i?id=191916602-12-72 . http://im2-tub-ru.yandex.net/i?id=337964418-03-72 .
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slide 2
Dispersion of light (decomposition of light) is a phenomenon due to 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 velocity of light in a substance on the wavelength (or frequency). Experimentally discovered by Newton around 1672, although theoretically well explained much later.
slide 3
One of the most illustrative examples of dispersion is the decomposition of white light as it passes through a prism (Newton's experiment).
slide 4
The essence of the phenomenon of dispersion is the unequal speed of propagation of light rays with different wavelengths in a transparent substance - an optical medium (whereas in vacuum the speed of light is always the same, regardless of the wavelength and hence the color). Usually, the higher the frequency of the wave, the greater the refractive index of the medium and the lower its speed of light in it: - red has the maximum speed in the medium and the minimum degree of refraction, - violet has the minimum speed of light in the medium and the maximum degree of refraction.
slide 5
Everyone has seen a rainbow in the sky at least once in their life. However, why do we distinguish colors? Why do we see grass green, sky blue, snow white, and earth black?
slide 6
In order to see light, two things are needed: 1. a source of light, that is, light + an object illuminated by it; 2. a receiver of light (that is, radiation) - the eye.
Slide 7
Two different types of nerve cells (receptors), called cones and rods, respectively, are responsible for the color brightness perception of the human eye. The rods are "responsible" for black and white vision. Thanks to them, the eye can recognize objects in low light conditions. Cones are designed to recognize color information. Under normal lighting, we perceive color solely with the help of three varieties of "cones", each of which is sensitive to a certain range of the visible spectrum.
Slide 8
The information obtained with the help of visual receptors enters in the form of signals to the brain, which determines in what proportions: the receptors are excited, creating color perception on the basis of this.
Slide 9
Slide 10
Probably, many of you asked this question in your childhood: "Why do cats' eyes glow in the dark?" Now you probably already guessed - this is how the "cones" of a cat's eyes reflect the light falling on them at dusk.
slide 11
From a physical point of view, what we perceive as light is a set of electromagnetic waves of certain frequencies that are visible to the human eye. The entire visible range of radiation (white, daylight) can be divided into seven sections. each of which has its own color. All together they form the so-called spectrum, which we manage to observe from time to time in the form of a rainbow.
slide 12
Ordinary sunlight is scattered on the smallest droplets of water left in the air after rain. And as a result, we see a rainbow. When water droplets disappear from the air after rain, all seven colors of the rainbow will again merge into one white daylight.
