Facts about Light
In ancient India, the philosophical schools of Samkhya and Vaisheshika, from around the sixth to fifth centuries B.C.E., developed theories on light.
Maxwell discovered that self-propagating electromagnetic waves would travel through space at a constant speed, which happened to be equal to the previously measured speed of light.
The observation and study of optical phenomena such as rainbows and the aurora borealis offer many clues about the nature of light as well as much enjoyment.
Christiaan Huygens worked out his own wave theory of light in 1678, and published it in his Treatise on light in 1690.
Reflection of light by a mirror is the basic example of specular reflection.
Some substances emit light slowly after excitation by more energetic radiation.
In 1905, Albert Einstein resolved this paradox by revising the Galilean model of space and time to account for the constancy of the speed of light.
Later, Augustin-Jean Fresnel independently worked out his own wave theory of light and presented it to the Acadйmie des Sciences in 1817.
A good early experiment to measure the speed of light was conducted by Ole Rшmer, a Danish physicist, in 1676.
According to the Samkhya school, light is one of the five fundamental "subtle" elements (tanmatra) out of which emerge the gross elements.
The speed of light depends upon the medium in which it is traveling, and the speed will be lower in a transparent medium.
The refraction quality of lenses is frequently used to manipulate light in order to change the apparent size of images.
Alhacen held light rays to be streams of minute particles that traveled at a finite speed.
Atoms absorb and emit light at characteristic frequencies, corresponding to particular energies.
The effects of the diffraction of light were first carefully observed and characterized by Francesco Maria Grimaldi.
When living things emit visible light, the process is called bioluminescence.
Renй Descartes (1596-1650) held that light was a disturbance of the plenum, the continuous substance of which the universe was composed.
When light strikes a rough or granular surface, it bounces off in all directions due to irregularities of the interface.
Another, more accurate, measurement of the speed of light was performed in Europe by Hippolyte Fizeau in 1849.
Knowing the distance to the mirror, the number of teeth on the wheel, and the rate of rotation, Fizeau was able to calculate the speed of light as 313,000,000 m/s.
The quantum mechanical theory of light and electromagnetic radiation continued to evolve through the 1920s and 1930s, culminating with the development during the 1940s of the theory of quantum electrodynamics, or QED.
Diffraction in the atmosphere by small particles in it can produce a bright ring around a bright light source such as the Sun or the Moon.
Reflection of light may be specular (that is, mirror-like) or diffuse (that is, not retaining the image, only the energy) depending on the nature of the interface between the two media.
Albert Camus (November 7, 1913 – January 4, 1960) was an Algerian-French writer and philosopher.
The sensory perception of light plays a central role in spirituality (vision, enlightenment, darshan, and Tabor Light).
Later in 499, Aryabhata, who proposed a heliocentric Solar System in his Aryabhatiya, wrote that the planets and the Moon do not have their own light but reflect the light of the Sun.
The reflection of visible light allows us to see objects that do not produce their own light.
Newton's corpuscular theory implied that light would travel faster in a denser medium, while the wave theory of Huygens and others implied the opposite.
Explaining his results by interference of the waves emanating from the two different slits, he deduced that light must propagate as waves.
Ptolemy (circa second century) wrote about the refraction of light, and developed a theory of vision that objects are seen by rays of light emanating from the eyes.
Nevertheless, several independent experiments showed that the energy imparted by light to atoms depends only on the light's frequency, not on its intensity.
where v denotes the speed that light travels in the transparent medium.
From this, Maxwell concluded that light was a form of electromagnetic radiation: he first stated this result in 1862 in On Physical Lines of Force.
Faraday's work inspired James Clerk Maxwell to study electromagnetic radiation and light.
Pierre Gassendi (1592-1655), an atomist, proposed a particle theory of light that was published posthumously in the 1660s.
Other physicists sought to explain the anomalous observations by semiclassical models, in which light is still described by Maxwell's equations, but the material objects that emit and absorb light are quantized.
When light from a compact source falls on a larger solid object, the shadow of the object shows small fringes near its edges.
The speed of light in a vacuum is exactly 299,792,458 meters per second (m/s) (about 186,282.397 miles per second).
Light rays are taken to be a stream of high-velocity of tejas (fire) atoms.
The weakness of the wave theory was that light waves, like sound waves, would need a medium for transmission.
Around the first century B.C.E., the Vishnu Purana refers to sunlight as the "the seven rays of the sun."
Faraday proposed in 1847 that light was a high-frequency electromagnetic vibration, which could propagate even in the absence of a medium such as the ether.
A rotating cog wheel was placed in the path of the light beam as it traveled from the source, to the mirror and then returned to its origin.
Maxwell's theory predicted that the energy of a light wave depends only on its intensity, not on its frequency.
The wave theory predicted that light waves could interfere with each other like sound waves (as noted around 1800 by Thomas Young), and that light could be polarized.
In 1637, he published a theory of the refraction of light that assumed, incorrectly, that light traveled faster in a denser medium than in a less dense medium.
Some substances produce light when they are illuminated by more energetic radiation, a process known as fluorescence.
The return of light into the medium from which it came is called reflection.
One of Newton's arguments against the wave nature of light was that waves were known to bend around obstacles, but light traveled only in straight lines.
The presence of light as opposed to its absence (darkness) is a common metaphor for good versus evil, knowledge versus ignorance, and similar concepts.
Galileo came into conflict with the Roman Catholic Church of his day because of the Church's endorsement of geocentric cosmology and opposition to the heliocentric view.
Isaac Newton studied these effects and attributed them to inflexion of light rays.
Consequently, Descartes' theory is often regarded as the forerunner of the wave theory of light.
Al-Haytham also correctly argued that we see objects because the Sun's rays of light, which he believed to be streams of tiny particles traveling in straight lines, are reflected from objects into our eyes.
The photon model accounted for the frequency dependence of light's energy, and it explained the ability of matter and radiation to be in thermal equilibrium.
The particles of light can exhibit different characteristics, depending on the speed and the arrangements of the tejas atoms.
Different physicists have attempted to measure the speed of light throughout history.
According to the current scientific concept of light, it is composed of elementary particles called photons, which can exhibit certain properties of both waves and particles.
Noting discrepancies in the apparent period of Io's orbit, Rшmer calculated that light takes about 18 minutes to traverse the diameter of Earth's orbit.
When a beam of light crosses the boundary between a vacuum and another medium, or between two different media, the wavelength of the light changes, but the frequency remains constant.
Given that light (electromagnetic radiation) has wave-like properties, it undergoes diffraction.
Particles moving through a medium faster than the speed of light in that medium can produce visible Cherenkov radiation.
The wavelength is calculated by determining the distance between corresponding points on consecutive waves. ... However, wavelengths can be as small as one billionth of a meter, like in gamma rays. They can also be as long as centimeters or meters, like in radio waves. Light waves are just part of the wave spectrum.
When the electron gains energy it moves to a higher energy level, then drops back to the ground state releasing its excess energy as light.The upper animation shows how blue (higher energy) light and the animation to the left shows how red (lower energy)light is created.
Old-style electric lamps work this way too. They make light by passing electricity through a very thin wire filament so it gets incredibly hot. Excited atoms inside the hot filament turn the electrical energy passing through them into light you can see by constantly giving off photons.May 7, 2017
They continued to study its behavior and decided that it probably travels in both waves and particles. Unlike sound, light doesn't need matter to help it along - it can travel through empty space, which is why the sun's light can get to us from outer space.Jun 19, 2017
Light travels so fast because it has no mass. The particles that make up electromagnetic radiation are called photons. Each photon has a packet or quantum of energy depending on the frequency of the radiation. The photon also has some momentum, but its mass is zero.
When you look at a banana, the wavelengths of reflected light determine what color you see. The light waves reflect off the banana's peel and hit the light-sensitive retina at the back of your eye. That's where cones come in. Cones are one type of photoreceptor, the tiny cells in the retina that respond to light.Apr 29, 2010
Light is the plants' only source of energy, so they are entirely dependent on light. Unlike people and animals who derive energy from carbohydrates, protein and fat, plants produce these substances using the energy from light and from carbon dioxide in the air.
Light is Life. We cannot imagine our life without light. ... It is the most important factor that influenced the way life evolved on Earth. From photosynthesis, which is responsible for making food in plants to the beautiful world we see and to meeting our energy requirements, the Sun is pivotal to our life.Jan 16, 2015
The light bulbs impact on society was that people now had light at all times of the day and did not need to rely on sunlight. Before the invention of the light bulb, people mainly used candles and gas lanterns for light when it was dark. ... After the light bulb was introduced, work could last much longer into the day.Dec 7, 2016
Edison made the first public demonstration of his incandescent light bulb on December 31, 1879, in Menlo Park. It was during this time that he said: "We will make electricity so cheap that only the rich will burn candles."
Most of these secretive lights are nothing more than a ploy to catch fishermen and have little to do with actually attracting catfish. Night fishing with lights in or shining on the water is a pretty common practice for many species of fish. The lights draw in bugs and bait fish which in turns can draw in fish.
Electromagnetic waves are made of oscillating magnetic and electric fields and, like all waves, they carry energy. There are many types of electromagnetic waves. From lowest energy to highest energy (red to blue) there are radio waves, microwaves, infrared, visible light, ultraviolet, x-rays and gamma rays.
Cones in our eyes are receivers for these tiny visible light waves. The Sun is a natural source for visible light waves and our eyes see the reflection of this sunlight off the objects around us. The color of an object that we see is the color of light reflected. All other colors are absorbed.
Bright bands formed where two wave crests overlapped and added together. ... The fields vibrate at right angles to the direction of movement of the wave, and at right angles to each other. Because light has both electric and magnetic fields, it's also referred to as electromagnetic radiation.
On the first night of Hanukkah, place a candle in the holder on the far right, and light it with the shamash. Then put the shamash back in its spot (leaving it lit). On the second night, light the candle second from the right, then the candle on the far right, and replace the lit shamash.
The moon has no light of its own. It reflects the sun's light. At any time, half of the Earth and half of the moon are lit by the sun. The other half is in shadow!