The first scientific hypotheses about the nature of light were expressed in the 17th century. By this time, two remarkable properties of light had been discovered - straightness of propagation in a homogeneous medium and independence of propagation of light beams, i.e. absence of influence of one light beam on the propagation of another light beam.
I. Newton in 1672 suggested the corpuscular nature of light. Newton's contemporaries, R. Hooke and H. Huygens, who developed the wave theory of light, opposed the corpuscular theory of light.
Speed of light. The first great advance in the study of the nature of light was the measurement of the speed of light.
The simplest way to measure the speed of light is to measure the time it takes a light signal to travel over a known distance.
However, attempts to carry out this kind of experiments ended in failure; no retardation of light could be detected even at a distance of several kilometers from the mirror.
For the first time, the speed of light was determined experimentally using the astronomical method. Danish scientist Olaf Roemer (1644-1710) in 1676. he discovered that when the distance between the Earth and the planet Jupiter changes due to their revolution around the Sun, the periodicity of the appearance of Jupiter's satellite Io of its shadow changes. In the case when the Earth is on the other side of the Sun in relation to Jupiter, the satellite Io appears from behind Jupiter 22 minutes later than it should happen according to calculations. But the satellites orbit the planets evenly, and therefore this delay is apparent. Roemer guessed that the reason for the delay in the appearance of Jupiter's satellite as the distance between the Earth and Jupiter increases is the finite speed of light. Thus, he was able to determine the speed of light.
Definition of light
Light is electromagnetic radiation that is invisible to the eye. Light becomes visible when it hits a surface. Colors are formed from waves of different lengths. All colors together form white light. When refracted light beam in a prism or drop of water, the entire spectrum of colors becomes visible, such as a rainbow. The eye perceives a range of visible light, 380 - 780 nm, beyond which there are ultraviolet (UV) and infrared (IR) light.
The emergence of the theory of light
In the 17th century, two theories of light arose: wave and corpuscular. The corpuscular theory was proposed by Newton, and the wave theory by Huygens. According to Huygens' ideas, light is a wave propagating in a special medium, the ether, which fills all space. The two theories existed in parallel for a long time. If according to one of the theories it was impossible to explain a phenomenon, then according to the other this phenomenon could be explained. This is why these two theories existed parallel to each other for so long.
For example: the rectilinear propagation of light, leading to the formation of sharp shadows, could not be explained on the basis of the wave theory. However, in early XIX centuries, such phenomena as diffraction and interference were discovered, which gave rise to thoughts that wave theory finally defeated the corpuscular one. In the second half of the 19th century, Maxwell showed that light special case electromagnetic waves. These works served as the foundation for electromagnetic theory Sveta. However, at the beginning of the 20th century it was discovered that when light is emitted and absorbed, it behaves like a stream of particles.
Corpuscular theory
Emissive (corpuscular): light consists of small particles (corpuscles) emitted by a luminous body. This opinion was supported by the straightness of light propagation, on which geometric optics is based, but diffraction and interference did not fit well into this theory. This is where the wave theory comes from.
Wave theory
Wave: light is a wave in the invisible world ether. Newton's opponents (Hooke, Huygens) are often called supporters of the wave theory, but it must be borne in mind that by wave they did not mean a periodic oscillation, as in modern theory, but a single impulse; for this reason, their explanations of light phenomena were hardly plausible and could not compete with Newton’s (Huygens even tried to refute diffraction). Developed wave optics appeared only at the beginning of the 19th century.
Newton is often considered a proponent of the corpuscular theory of light; in fact, as usual, he “did not invent hypotheses” and readily admitted that light could also be associated with waves in the ether. In a treatise presented to the Royal Society in 1675, he writes that light cannot be simply vibrations of the ether, since then it could, for example, travel through a curved pipe, as sound does. But, on the other hand, he suggests that the propagation of light excites vibrations in the ether, which gives rise to diffraction and other wave effects. Essentially, Newton, clearly aware of the advantages and disadvantages of both approaches, puts forward a compromise, particle-wave theory of light. In his works, Newton described in detail the mathematical model of light phenomena, leaving aside the question of the physical carrier of light: “My teaching about the refraction of light and colors consists solely in establishing certain properties of light without any hypotheses about its origin.” Wave optics, when it appeared, did not reject Newton's models, but absorbed them and expanded them on a new basis.
Despite his dislike of hypotheses, Newton included at the end of Optics a list of unsolved problems and possible answers to them. However, in these years he could already afford this - Newton’s authority after “Principia” became indisputable, and few people dared to bother him with objections. A number of hypotheses turned out to be prophetic. Specifically, Newton predicted:
deflection of light in a gravitational field;
the phenomenon of polarization of light;
interconversion of light and matter.
Brighten up your science knowledge with our fun easy facts for kids. Enjoy fun trivia related to the speed of light, optics, sunlight, ultraviolet light and infrared light. Understand how electromagnetic radiation works and discover many fascinating properties of light.
In physics, light refers to electromagnetic radiation. The light we usually talk about in Everyday life, refers to the visible spectrum (part electromagnetic spectrum which the human eye can see).
Other animals can see parts of the spectrum that humans cannot. For example, a large number of insects can see ultraviolet (UV) light.
Ultraviolet light can be used to show things that the human eye cannot see, useful for forensic scientists.
The wavelength of infrared light is too long to be visible to the human eye.
Scientists study the properties and behavior of light in the branch of physics known as optics.
Isaac Newton noticed that a thin ray of sunlight hitting a glass prism at an angle creates a streak visible colors, including red, orange, yellow, green, blue, indigo and violet (ROYGBIV). This happened because different colors pass through glass (and other media) with at different speeds, causing them to refract under different angles and separate from each other.
Light travels very, very quickly. The speed of light in a vacuum (a region free of matter) is about 186,000 miles per second (300,000 kilometers per second).
Light travels slower with different environments such as glass, water and air. These media are given a refractive index to describe how much they slow down the movement of light. Glass has a refractive index of 1.5, which means lights travel through it at about 124,000 miles per second (200,000 kilometers per second). The refractive index of water is 1.3 and the refractive index of air is 1.0003, which means that air slows down light only slightly.
Light takes 1.255 seconds to travel from the Earth to the Moon.
Sunlight can reach depths of about 80 meters (262 feet) in the ocean.
One of the many things Italian scientist Galileo Galilei worked on were telescopes, producing telescopes with 30x magnification in some of his later work. These telescopes helped him discover four largest moons, orbiting Jupiter (later called the satellites of Galileo).
Photosynthesis is a process that involves plants using energy from sunlight to convert carbon dioxide for food.
Plan: First information about light in ancient period.
Creation of the foundations of geometric optics (Euclid,
Archimedes, Ptolemy, Lucretius Carus).
Development of the doctrine of light during the Middle Ages
(Roger Bacon) and in the Renaissance (Leonardo
da Vinci, Porta).
Development of the doctrine of light in the 17th century (Kepler, Hooke,
Huygens, Galileo, Fermi). Creation began
wave optics and the first optical instruments
(Lippershey, Galileo, Leeuwenhoek).
Development of optics in the 19th century. Creation
theoretical and experimental foundations
wave optics (Jung, Fresnel, Stefan,
Boltzmann, Wien, Maxwell, Michelson).
1. The first information about light in the ancient period. Creation of the foundations of geometric optics (Euclid, Archimedes, Ptolemy, Lucretius Carus).
Already in the 3rd century BC. e. has developed geometric optics, basicswhich are set out in the works of the famous Euclid (300 BC.
BC), summarizing the empirical data of predecessors
(works “optics” and “catoptrics”). Following Plato, Euclid
shares the theory of optic rays. These rays are straight lines.
The visibility of an object is due to the fact that from the eye, as from
vertices, there is a contour of rays, the forming of which
directed tangentially to the boundary of the object. Magnitude
the object is determined from angular view.
In “optics” the law of rectilinearity is formed for the first time
propagation of light.
Euclid's Catoptrics discusses the phenomenon of reflection
Sveta. The law of light reflection is formulated here. This law
applicable to both flat and spherical mirrors. Legend attributes it to Archimedes
burning of the Roman fleet with
concave mirrors. The ancients knew
the effect of lenses, more precisely glass
balls. Thus, the playwright Aristophanes,
contemporary of Socrates, advises
the debtor to melt the debt
commitment written on wax
tablet, with the help of an incendiary
glass Ptolemy (19th-ca. 160th century BC) explored
refraction of light using (disc)
instrument, but he did not find the law of refraction.
Lucretius Carus (94-51 BC) in his
the poem “On the Nature of Things” interprets light as
some material substrate. We are in it
we find a prototype of corpuscular nature
Sveta.
From the poem it is clear that he was familiar with the law
light reflections:
“... makes everything bounce off things
nature and is reflected back under the same
angle as it fell.”
2. Development of the doctrine of light during the Middle Ages (Roger Bacon) and during the Renaissance (Leonardo da Vinci, Porta).
During the Middle Ages, optics did not receive any development,with the exception of statements and observations of light phenomena
in the works of Roger Bacon dating back to the 13th century.
Roger Bacon explained the appearance of the rainbow by refraction
raindrops; I advised people with low vision to apply
a convex lens to the eye.
During the Renaissance (XV-XVI centuries) a significant contribution to
Optics was developed by Leonardo da Vinci. He first established that
the eye is fundamentally similar to a camera obscura. He explained
stereoscopic vision with two eyes. He owns
first ideas about wave motion.
3. Development of the doctrine of light in the 17th century (Kepler, Hooke, Huygens, Galileo, Fermi). Creation of the beginnings of wave optics and the first optical instruments (Lippe
3. Development of the doctrine of light in the 17th century (Kepler, Hooke, Huygens,Galileo, Fermi). Creation of the beginnings of wave optics and
the first optical instruments (Lippershey, Galileo,
Leeuwenhoek).
In the 17th century, optics experienced an exceptional flourishing. TO
by the end of the century it turned into a developed powerful industry
physical science along with mechanics, delivered
the only reliable material for theoretical
generalizations.
During this period, a theoretical struggle unfolded around
question about the nature of light.
The heyday of optics began with the improvement of methods
grinding optical glasses and searching for magnifying tubes. In 1608, the Dutchman Lippershey filed
application for a patent for
spotting scope.
Galileo (1564-1642), hearing about the trumpet,
began to think about its possible
device and independently
made what is now called the pipe
Galilee. It is used in binoculars.
4. Development of optics in the 19th century. Creation of the theoretical and experimental foundations of wave optics (Jung, Fresnel, Stefan, Boltzmann, Wien, Maxwell,
Michelson).In the 19th century, great contributions were made to the development of the doctrine of light
scientists Jung and Boltzmann, . Let's take a look at their work.
Young Thomas (1773-1829) - English scientist, one of
creators of wave optics, member of the Royal
society and its secretary (1802-1829). At the age of 2 he began to read,
discovering a phenomenal memory. At the age of 4 I knew it by heart
works of many English poets, at the age of 8-9 mastered
turning skills, crafted various physical
instruments, at the age of 14 he became acquainted with differential
Calculus (according to Newton), studied many languages. Studied at
University of London, Edinburgh and Gettyn, in
At first I studied medicine, then I became interested in physics, in particular,
optics and acoustics. AB last years engaged in life
compilation of an Egyptian dictionary. In 1793 he explained the phenomenon of eye accommodation by a change
curvature of the lens
2. In 1800 he defended the theory of light.
3. In 1801 he explained the phenomenon of interference of light and a ring
Newton.
4. In 1803 he introduced the term “interference”.
5. In 1803, he made an attempt to explain the diffraction of light from
thin thread, linking it with interference.
6. Showed that when a ray of light is reflected from a denser
surface there is a loss of half-wave.
7. Measured wavelengths different colors, got for length
waves of red color are 0.7 microns, for violet - 0.42.
8. Expressed the idea (1807) that light and radiant heat
They differ from each other only in wavelength.
9. In 1817 he put forward the idea of transverse light waves. Boltzmann Ludwig (1844-1906) - Austrian physicist - theorist,
member of the Austrian and corresponding member. Petersburg Academy of Sciences.
In 1866 he introduced the law of distribution of gas molecules over
speeds (Boltzmann statistics).
In 1872 he derived the basic equation of kinetic energy
gas:
p=2n m0 ˂v˃/2
3
where ˂v˃ – average speed molecules, m0- molecular mass, nconcentration of molecules (number of molecules per unit volume
gas).
In 1872 he proved the statistical nature of the 2nd principle
thermodynamics, showed the inconsistency of the thermal hypothesis
death of the Universe.
For the first time he applied the principles of thermodynamics to the study. I use J. Maxwell's hypothesis about light pressure, in
1884 theoretically discovered the law of thermal radiation:
4
E=ßT, early (in 1879) experimentally established
Stefan (Stefan-Boltzmann law).
In 1884, from thermodynamic considerations he derived
existence of light pressure.
He defended the atomic theory.
The proportionality coefficient in Boltzmann is named after
equation:
p= knT,
-23
-1
equal to 1.380662*10
J*K, called constant
Boltzmann is one of the most important constants in physics, equal to
temperature ratio expressed in energy units
(joules), to the same temperature expressed in degrees
Kelvin:
k=2/3*m(0) (v)*2/2/T
Questions:
1.2.
3.
4.
5.
Who discovered the existence of mountains on the Moon and
depressions?
What is the name of Lucretius Cara's poem?
During which era did a significant contribution to
Did Leonardo da Vinci develop optics?
What term was used by Young Thomas in 1803?
Who invented the microscope and in what year?
Light is amazing phenomenon, he's straight and figuratively illuminates our lives in many ways.
The Sun is actually white when viewed from space because its light is not scattered by our atmosphere. From Venus you will not see the Sun at all, since the atmosphere there is too dense.
1
Humans are bioluminescent due to metabolic reactions, but our glow is 1000 times weaker than what can be seen with the naked eye.
2
Sunlight can penetrate approximately 80 meters into the ocean. If you go 2000 meters deeper, you can find a bioluminescent monkfish that lures its victims with glowing flesh.
3
Plants are green because they reflect green light and absorb other colors for photosynthesis. If you place a plant under green light, it will most likely die.
4
North and South Polar Lights occurs when the "wind" from solar flares interacts with particles earth's atmosphere. According to Eskimo legends, the aurora is the souls of the dead playing football with the head of a walrus.
5
In 1 second, the Sun emits enough energy to provide the entire world with it for a million years.
6
The longest burning lamp in the world is a century-old lamp in a California fire department. It has been continuously burning since 1901.
7
Light sneeze reflex, which causes uncontrollable sneezing attacks in the presence of bright light, occurs in 18-35 percent of people, although no one can explain why it occurs. One way to deal with it is to wear sunglasses.
8
In a double rainbow, light is reflected twice inside each drop of water, and the colors in the outer rainbow are in reverse order.
9
Some animals see light that we cannot see. Bees see ultraviolet light, while rattlesnakes see infrared light.
10
Niagara Falls was first electrically illuminated in 1879, illuminating the equivalent of 32,000 candles. Today, the illumination of Niagara Falls is equivalent to the illumination of 250 million candles.
11
When the light comes through different substances, it slows down and refracts. Thus, the lens focuses the rays at one point and can set the paper on fire.
12
Light has momentum. Scientists are developing ways to harness this energy for long-distance space travel.
13
Frog eyes are so sensitive to light that researchers in Singapore are using them to develop incredibly accurate photon detectors.
14
Visible light is only part of the electromagnetic spectrum that our eyes see. This is why LED lamps are so economical. Unlike incandescent bulbs, LED bulbs only emit visible light.
15
Fireflies emit a cool glow through chemical reaction with 100% efficiency. Scientists are working to imitate fireflies to create more energy-efficient LEDs.
16
To study how our eyes perceive light, Isaac Newton inserted needles into the eye socket. He tried to understand whether light is the result of something coming from outside or from within. (Answer: both assumptions are correct, since the rods in the eyes react to certain frequencies).
17
If the Sun suddenly came to an end, no one on Earth would notice it for another 8 minutes and 17 seconds. This is the time it takes sunlight to reach Earth. But don't worry, the Sun has another 5 billion years of fuel left.
18
Despite their name, black holes are actually the most... bright objects in the Universe. Even though we cannot see beyond the event horizon, they can generate more energy than the galaxies in which they are located.
19
A rainbow occurs when light encounters water droplets in the air, refracts and reflects within the droplet, and refracts again, leaving it behind.
20
Light is an amazing phenomenon; it literally and figuratively illuminates our lives in many ways. UN announced 2015 International Year light to demonstrate to "the inhabitants of the Earth the importance of light and optical technologies in life, for the future and for the development of society." Here are a few interesting facts about light that you may not have known about.
sunlight1. The sun is actually white when viewed from space because its light is not scattered by our atmosphere. From Venus you will not see the Sun at all, since the atmosphere there is too dense.
2. Humans are bioluminescent due to metabolic reactions, but our glow is 1000 times weaker than what can be seen with the naked eye.
3. Sunlight can penetrate approximately 80 meters into the ocean. If you go 2000 meters deeper, you can find a bioluminescent monkfish that lures its victims with glowing flesh.
4. Plants are green because they reflect green light and absorb other colors for photosynthesis. If you place a plant under green light, it will most likely die.
5. The northern and southern aurora occur when the “wind” from solar flares interacts with particles in the Earth’s atmosphere. According to Eskimo legends, the aurora is the souls of the dead playing football with the head of a walrus.
6. In 1 second, the Sun emits enough energy to provide the entire world with it for a million years.
7. The longest burning lamp in the world is a century-old lamp in a California fire department. It has been continuously burning since 1901.
8. The light sneeze reflex, which causes uncontrollable bouts of sneezing in the presence of bright light, occurs in 18 to 35 percent of people, although no one can explain why it occurs. One way to deal with it is to wear sunglasses.
9. In a double rainbow, light is reflected twice inside each drop of water, and the colors in the outer rainbow are in reverse order.
10. Some animals see light that we cannot see. Bees see ultraviolet light, while rattlesnakes see infrared light.
11. Niagara Falls was first electrically lit in 1879, with the illumination equivalent of 32,000 candles. Today, the illumination of Niagara Falls is equivalent to the illumination of 250 million candles.
12. When light passes through different substances, it slows down and is refracted. Thus, the lens focuses the rays at one point and can set the paper on fire.
Laws of light
13. Light has momentum. Scientists are developing ways to harness this energy for long-distance space travel.
14. Frog eyes are so sensitive to light that researchers in Singapore are using them to develop incredibly accurate photon detectors.
15. Visible light is only part of the electromagnetic spectrum that our eyes see. This is why LED lamps are so economical. Unlike incandescent bulbs, LED bulbs only emit visible light.
16. Fireflies emit a cool glow through a chemical reaction with 100% efficiency. Scientists are working to imitate fireflies to create more energy-efficient LEDs.
17. To study how our eyes perceive light, Isaac Newton inserted needles into the eye socket. He tried to understand whether light is the result of something coming from outside or from within. (Answer: both assumptions are correct, since the rods in the eyes react to certain frequencies).
18. If the Sun suddenly came to an end, no one on Earth would notice it for another 8 minutes 17 seconds. This is the time it takes for sunlight to reach the Earth. But don't worry, the Sun has another 5 billion years of fuel left.
19. Despite their name, black holes are actually the brightest objects in the Universe. Even though we cannot see beyond the event horizon, they can generate more energy than the galaxies in which they are located.
20. A rainbow occurs when light encounters water droplets in the air, is refracted and reflected within the droplet, and is refracted again, leaving it behind.
