An
optical phenomenon is any observable event that results from the interaction of
lightLight or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
and
matterMatter is a general term for the substance of which all physical objects consist. Typically, matter includes atoms and other particles which have mass. A common way of defining matter is as anything that has mass and occupies volume...
. See also
list of optical topics and
opticsOptics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
. A
mirageA mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky. The word comes to English via the French mirage, from the Latin mirare, meaning "to look at, to wonder at"...
is an example of an optical phenomenon.
Common optical phenomena are often due to the interaction of light from the sun or moon with the atmosphere, clouds, water, dust, and other particulates. One common example is the
rainbowA rainbow is an optical and meteorological phenomenon that causes a spectrum of light to appear in the sky when the Sun shines on to droplets of moisture in the Earth's atmosphere. It takes the form of a multicoloured arc...
, when light from the sun is reflected and refracted by water droplets. Some, such as the green ray, are so rare they are sometimes thought to be mythical. Others, such as
Fata MorganaA Fata Morgana is an unusual and very complex form of mirage, a form of superior mirage, which, like many other kinds of superior mirages, is seen in a narrow band right above the horizon...
s, are commonplace in favored locations.
Other phenomena are simply interesting aspects of
opticsOptics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
, or optical effects. The colors generated by a
prismIn optics, a dispersive prism is a type of optical prism, normally having the shape of a geometrical triangular prism. It is the most widely-known type of optical prism, although perhaps not the most common in actual use. Triangular prisms are used to disperse light, that is, to break light up into...
are often shown in classrooms, for instance.
A list of optical phenomena
Optical phenomena include those arising from the optical properties of the
atmosphereAn atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
; the rest of nature (other phenomena); of
objectsIn physics, a physical body or physical object is a collection of masses, taken to be one...
, whether natural or human-made (optical effects); and of our
eyeThe human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
s (Entoptic phenomena). Also listed here are unexplained phenomena that could have an optical explanation and "
optical illusionAn optical illusion is characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a perception that does not tally with a physical measurement of the stimulus source...
s" for which optical explanations have been excluded.
There are many phenomena that result from either the
particleIn physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
or the
waveElectromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...
nature of light. Some are quite subtle and observable only by precise measurement using scientific instruments. One famous observation is of the bending of light from a star by the
SunThe Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
observed during a solar eclipse. This demonstrates that
spaceIn physics, spacetime is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space as being three-dimensional and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions...
is curved, as the
theory of relativityThe theory of relativity, or simply relativity, encompasses two theories of Albert Einstein: special relativity and general relativity. However, the word relativity is sometimes used in reference to Galilean invariance....
predicts.
Observations of some phenomena such as the
photoelectric effectIn the photoelectric effect, electrons are emitted from matter as a consequence of their absorption of energy from electromagnetic radiation of very short wavelength, such as visible or ultraviolet light. Electrons emitted in this manner may be referred to as photoelectrons...
, which is the flow of electric current in a material or through a vacuum (as in a photocell) when the material is exposed to light, led to advances in science, since they could not be easily explained by existing theory.
Atmospheric optical phenomena
- Afterglow
An afterglow is a broad high arch of whitish or rosy light appearing in the sky due to very fine particles of dust suspended in the high regions of the atmosphere. An afterglow may appear above the highest clouds in the hour of deepening twilight, or reflected from the high snowfields in mountain...
- Airglow
Airglow is the very weak emission of light by a planetary atmosphere. In the case of Earth's atmosphere, this optical phenomenon causes the night sky to never be completely dark .-Development:The airglow phenomenon was first identified in 1868 by Swedish scientist...
- Alexander's band
thumb|200px|Ray paths of the primary rainbowthumb|200px|Ray paths of the secondary rainbowthumb|400px|Alexander's BandAlexander's band or Alexander's dark band is an optical phenomenon associated with rainbows which was named after Alexander of Aphrodisias who first described it. It occurs due to...
, the dark region between the two bows of a double rainbow.
- Alpenglow
Alpenglow is an optical phenomenon. When the Sun is just below the horizon, a horizontal red glowing band can sometimes be observed on the opposite horizon...
- Anticrepuscular rays
Anticrepuscular rays are similar to crepuscular rays, but seen opposite the sun in the sky. Anticrepuscular rays are near-parallel, but appear to converge at the antisolar point because of linear perspective. Anticrepuscular rays are most frequently visible near sunrise or sunset. Crepuscular rays...
- Auroral light (northern and southern lights, aurora borealis and aurora australis)
- Belt of Venus
The Belt of Venus or Venus's Girdle is the Victorian-era name for an atmospheric phenomenon seen at sunrise and sunset. Shortly after sunset or shortly before sunrise, the observer is, or is very nearly, surrounded by a pinkish glow or antitwilight arch that extends roughly 10°–20° above the horizon...
- Blue Flash
- Blue moon
A blue moon can refer to the third full moon in a season with four full moons. Most years have twelve full moons that occur approximately monthly. In addition to those twelve full lunar cycles, each solar calendar year contains roughly eleven days more than the lunar year of 12 lunations...
- Circumzenithal arc
The circumzenithal arc or circumzenith arc , also called the Bravais' arc, is an optical phenomenon similar in appearance to a rainbow; but it arises from refraction of sunlight through horizontally-oriented ice crystals, generally in cirrus clouds, rather than from raindrops...
- Crepuscular rays
Crepuscular rays , in atmospheric optics, are rays of sunlight that appear to radiate from a single point in the sky. These rays, which stream through gaps in clouds or between other objects, are columns of sunlit air separated by darker cloud-shadowed regions...
- Earthquake lights
- Earth's shadow
The Earth's shadow or Earth shadow are names for the shadow that the Earth itself casts on its atmosphere. This shadow is often visible from the surface of the Earth, as a dark band in the sky near the horizon...
- Glories
A glory is an optical phenomenon that resembles an iconic saint's halo about the shadow of the observer's head. The effect is produced by light backscattered towards its source by a cloud of uniformly sized water droplets...
(also known as Brocken's Specter or Specter of the Brocken)
- Green Flash
Green flashes and green rays are optical phenomena that occur shortly after sunset or before sunrise, when a green spot is visible, usually for no more than a second or two, above the sun, or it may resemble a green ray shooting up from the sunset point. Green flashes are a group of phenomena...
- Halos
A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
, of Sun or Moon, including sun dogA sun dog or sundog, scientific name parhelion ; , also called a mock sun or a phantom sun, is an atmospheric phenomenon that creates bright spots of light in the sky, often on a luminous ring or halo on either side of the sun.Sundogs may appear as a colored patch of light to the left or right of...
s
- Heiligenschein
Heiligenschein is an optical phenomenon which creates a bright spot around the shadow of the viewer's head. It is created when the surface on which the shadow falls has special optical characteristics. Dewy grass is known to exhibit these characteristics, and creates a Heiligenschein...
or halo effect, partly caused by the Opposition effect
- Cloud iridescence
thumb|260px|Cloud iridescenceCloud iridescence is the occurrence of colors in a cloud similar to those seen in oil films on puddles, and is similar to irisation. It is a fairly uncommon phenomenon, most often observed in altocumulus, cirrocumulus and lenticular clouds, and very rarely in Cirrus...
- Light pillar
A light pillar is a visual phenomenon created by the reflection of light from ice crystals with near horizontal parallel planar surfaces. The light can come from the Sun in which case the phenomenon is called a sun pillar or solar pillar...
- Rainbow
A rainbow is an optical and meteorological phenomenon that causes a spectrum of light to appear in the sky when the Sun shines on to droplets of moisture in the Earth's atmosphere. It takes the form of a multicoloured arc...
s
- Sundogs
- Mirage
A mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky. The word comes to English via the French mirage, from the Latin mirare, meaning "to look at, to wonder at"...
s (including Fata MorganaA Fata Morgana is an unusual and very complex form of mirage, a form of superior mirage, which, like many other kinds of superior mirages, is seen in a narrow band right above the horizon...
)
- Shadow set
- Tyndall effect
The Tyndall effect, also known as Tyndall scattering, is light scattering by particles in a colloid or particles in a fine suspension. It is named after the 19th century physicist John Tyndall. It is similar to Rayleigh scattering, in that the intensity of the scattered light depends on the fourth...
Other optical phenomena
- Dichromatism
Dichromatism is a phenomenon where the hue of the colour in materials or solutions are dependent on both the concentration of the absorbing substance and the depth or thickness of the medium traversed...
- Gegenschein
The gegenschein is a faint brightening of the night sky in the region of the antisolar point.- Explanation :Like the zodiacal light, the gegenschein is sunlight reflected by interplanetary dust...
- Iridescence
Iridescence is generally known as the property of certain surfaces which appear to change color as the angle of view or the angle of illumination changes...
- Opposition effect
- Sylvanshine
Sylvanshine is an optical phenomenon in which dew-covered trees of species whose leaves are wax-covered retroreflect beams of light, as from a vehicle's headlights, sometimes causing trees to appear to be snow-covered at night during the summer. The phenomenon was named and explained in 1994 by...
- Zodiacal light
Zodiacal light is a faint, roughly triangular, whitish glow seen in the night sky which appears to extend up from the vicinity of the sun along the ecliptic or zodiac. Caused by sunlight scattered by space dust in the zodiacal cloud, it is so faint that either moonlight or light pollution renders...
Optical effects
- Asterism
Asteria, or star stone is a name applied to ornamental stones that exhibit a luminous star when cut en cabochon. The typical asteria is the star-sapphire, generally a bluish-grey corundum, milky or opalescent, with a star of six rays...
, star gemsA gemstone or gem is a piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments...
such as star sapphireSapphire is a gemstone variety of the mineral corundum, an aluminium oxide , when it is a color other than red or dark pink; in which case the gem would instead be called a ruby, considered to be a different gemstone. Trace amounts of other elements such as iron, titanium, or chromium can give...
or star rubyA ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum . The red color is caused mainly by the presence of the element chromium. Its name comes from ruber, Latin for red. Other varieties of gem-quality corundum are called sapphires...
.
- Aura, a phenomenon in which gas or dust surrounding an object luminesces or reflects light from the object.
- Aventurescence
In gemology, aventurescence is an optical reflectance effect seen in certain gems. The effect amounts to a metallic glitter, arising from minute, preferentially oriented mineral platelets within the material. These platelets are so numerous that they also influence the material's body colour...
, also called the Schiller effect, spangled gems such as aventurine quartz and sunstoneSunstone is a plagioclase feldspar, which when viewed from certain directions exhibits a brilliant spangled appearance; this has led to its use as a gemstone. It has been found in Southern Norway, and in some United States localities...
.
- The camera obscura
The camera obscura is an optical device that projects an image of its surroundings on a screen. It is used in drawing and for entertainment, and was one of the inventions that led to photography. The device consists of a box or room with a hole in one side...
- Caustics
In optics, a caustic or caustic network is the envelope of light rays reflected or refracted by a curved surface or object, or the projection of that envelope of rays on another surface. The caustic is a curve or surface to which each of the light rays is tangent, defining a boundary of an...
- Chatoyancy
In gemology, chatoyancy , or chatoyance, is an optical reflectance effect seen in certain gemstones. Coined from the French "œil de chat," meaning "cat's eye," chatoyancy arises either from the fibrous structure of a material, as in tiger eye quartz, or from fibrous inclusions or cavities within...
, cat's eye gems such as chrysoberylThe mineral or gemstone chrysoberyl is an aluminate of beryllium with the formula BeAl2O4. The name chrysoberyl is derived from the Greek words χρυσός chrysos and βήρυλλος beryllos, meaning "a gold-white spar". Despite the similarity of their names, chrysoberyl and beryl are two completely...
cat's eye or aquamarineThe mineral beryl is a beryllium aluminium cyclosilicate with the chemical formula Be3Al26. The hexagonal crystals of beryl may be very small or range to several meters in size. Terminated crystals are relatively rare...
cat's eye
- Chromatic polarization
- Cathodoluminescence
Cathodoluminescence is an optical and electrical phenomenon whereby a beam of electrons is generated by an electron gun and then impacts on a luminescent material such as a phosphor, causing the material to emit visible light. The most common example is the screen of a television...
- Diffraction
Diffraction refers to various phenomena which occur when a wave encounters an obstacle. Italian scientist Francesco Maria Grimaldi coined the word "diffraction" and was the first to record accurate observations of the phenomenon in 1665...
, the apparent bending and spreading of light waveIn physics, a wave is a disturbance that travels through space and time, accompanied by the transfer of energy.Waves travel and the wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium—that is, with little or no associated mass...
s when they meet an obstruction.
- Dispersion
In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency, or alternatively when the group velocity depends on the frequency.Media having such a property are termed dispersive media...
- Double refraction or birefringence
Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...
of calciteCalcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
and other minerals
- The Double-slit experiment
The double-slit experiment, sometimes called Young's experiment, is a demonstration that matter and energy can display characteristics of both waves and particles...
- Electroluminescence
Electroluminescence is an optical phenomenon and electrical phenomenon in which a material emits light in response to the passage of an electric current or to a strong electric field...
- Evanescent wave
An evanescent wave is a nearfield standing wave with an intensity that exhibits exponential decay with distance from the boundary at which the wave was formed. Evanescent waves are a general property of wave-equations, and can in principle occur in any context to which a wave-equation applies...
- Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...
, also called luminescence or photoluminescencePhotoluminescence is a process in which a substance absorbs photons and then re-radiates photons. Quantum mechanically, this can be described as an excitation to a higher energy state and then a return to a lower energy state accompanied by the emission of a photon...
.
- Phosphorescence
Phosphorescence is a specific type of photoluminescence related to fluorescence. Unlike fluorescence, a phosphorescent material does not immediately re-emit the radiation it absorbs. The slower time scales of the re-emission are associated with "forbidden" energy state transitions in quantum...
- Mie scattering (Why clouds are white)
- Metamerism
In colorimetry, metamerism is the matching of apparent color of objects with different spectral power distributions. Colors that match this way are called metamers....
as of alexandrite
- Moire
- Newton's rings
The phenomenon of Newton's rings, named after Isaac Newton who first studied them in 1717, is an interference pattern caused by the reflection of light between two surfaces - a spherical surface and an adjacent flat surface...
- Pleochroism
Pleochroism is an optical phenomenon in which a substance appears to be different colors when observed at different angles with polarized light.- Background :Anisotropic crystals will have optical properties that vary with the direction of light...
gems or crystalA crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
s, which seem many-colored
- Polarized light-related phenomena such as double refraction, or Haidinger's brush
Haidinger's brush is an entoptic phenomenon first described by Austrianphysicist Wilhelm Karl von Haidinger in 1844.Many people are able to perceive polarization of light....
- Rayleigh scattering
Rayleigh scattering, named after the British physicist Lord Rayleigh, is the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light. The particles may be individual atoms or molecules. It can occur when light travels through...
(Why the sky is blue, sunsets are red, and associated phenomena)
- Refraction
Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed...
- Sonoluminescence
Sonoluminescence is the emission of short bursts of light from imploding bubbles in a liquid when excited by sound.-History:The effect was first discovered at the University of Cologne in 1934 as a result of work on sonar. H. Frenzel and H. Schultes put an ultrasound transducer in a tank of...
- Synchrotron radiation
The electromagnetic radiation emitted when charged particles are accelerated radially is called synchrotron radiation. It is produced in synchrotrons using bending magnets, undulators and/or wigglers...
- The separation of light into colors by a prism
- Triboluminescence
Triboluminescence is an optical phenomenon in which light is generated when material is pulled apart, ripped, scratched, crushed, or rubbed through the breaking of chemical bonds in the material. The phenomenon is not fully understood, but appears to be caused by the separation and reunification...
- The Zeeman effect
The Zeeman effect is the splitting of a spectral line into several components in the presence of a static magnetic field. It is analogous to the Stark effect, the splitting of a spectral line into several components in the presence of an electric field...
- Thomson Scattering
Thomson scattering is the elastic scattering of electromagnetic radiation by a free charged particle, as described by classical electromagnetism. It is just the low-energy limit of Compton scattering: the particle kinetic energy and photon frequency are the same before and after the scattering...
- Total internal reflection
Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary and the incident angle is...
- Twisted light
- The Umov effect
The Umov effect, also known as Umov's law, is a relationship between the albedo of an astronomical object, and the degree of polarization of light reflecting off it...
- The ability of light to travel through space or through a vacuum.
Entoptic phenomena
- Diffraction
Diffraction refers to various phenomena which occur when a wave encounters an obstacle. Italian scientist Francesco Maria Grimaldi coined the word "diffraction" and was the first to record accurate observations of the phenomenon in 1665...
of light through the eyelashes
- Floaters
- Haidinger's brush
Haidinger's brush is an entoptic phenomenon first described by Austrianphysicist Wilhelm Karl von Haidinger in 1844.Many people are able to perceive polarization of light....
- Monocular
A monocular is a modified refracting telescope used to magnify the images of distant objects by passing light through a series of lenses and sometimes prisms; the use of prisms results in a lightweight telescope. Volume and weight are less than half those of binoculars of similar optical...
diplopiaDiplopia, commonly known as double vision, is the simultaneous perception of two images of a single object that may be displaced horizontally, vertically, or diagonally in relation to each other...
(or polyplopia) from reflections at boundaries between the various ocular media
- Phosphene
A phosphene is a phenomenon characterized by the experience of seeing light without light actually entering the eye. The word phosphene comes from the Greek words phos and phainein...
s from stimulation other than by light (e.g., mechanical, electrical) of the rod cellRod cells, or rods, are photoreceptor cells in the retina of the eye that can function in less intense light than can the other type of visual photoreceptor, cone cells. Named for their cylindrical shape, rods are concentrated at the outer edges of the retina and are used in peripheral vision. On...
s and conesCone cells, or cones, are photoreceptor cells in the retina of the eye that are responsible for color vision; they function best in relatively bright light, as opposed to rod cells that work better in dim light. If the retina is exposed to an intense visual stimulus, a negative afterimage will be...
of the eye or of other neurons of the visual system
- Purkinje images
Purkinje images are reflections of objects from structure of the eye. They are also known as Purkinje reflexes and as Purkinje-Sanson images. There are at least four Purkinje images that are visible on looking at an eye. The first Purkinje image is the reflection from the outer surface of the cornea...
.
Optical illusions
- The unusually large size of the Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
as it rises and sets, the moon illusionThe Moon illusion is an optical illusion in which the Moon appears larger near the horizon than it does while higher up in the sky. This optical illusion also occurs with the sun and star constellations. It has been known since ancient times, and recorded by numerous different cultures...
- The shape of the sky, the sky bowl
Unexplained phenomena
Some phenomena are yet to be conclusively explained and may possibly be some form of optical phenomena. Some consider many of these "mysteries" to simply be local
tourist attractionA tourist attraction is a place of interest where tourists visit, typically for its inherent or exhibited cultural value, historical significance, natural or built beauty, or amusement opportunities....
s that are not worthy of thorough investigation.
- Marfa lights
The Marfa lights, also known as the Marfa ghost lights, have been observed near U.S. Route 67 on Mitchell Flat east of Marfa, Texas, in the United States...
- Hessdalen light
The Hessdalen Light is unexplained light usually seen in the Hessdalen valley in the municipality of Holtålen in Sør-Trøndelag county, Norway.-History and description:Unusual lights have been reported here since 1940s or earlier...
s
- Min Min light
Min Min Light is the name given to an unusual light formation that has been reported numerous times in eastern Australia. The lights have been reported from as far south as Brewarrina in western New South Wales, to as far north as Boulia in northern Queensland...
s
- Light of Saratoga
The "Light of Saratoga" is a legend located in the Big Thicket of Southeast Texas. This legend of a mysterious light is also known as the "Ghost Road" of Saratoga, the "Saratoga Light", and "Bragg Road Ghost Light" by local residents...
- Naga fireballs
The Naga fireballs , also referred to as Mekong lights, are a phenomenon seen in the Mekong river—in Thailand and in Laos —in which glowing balls rise from the water high into the air...
Further reading
- Thomas D. Rossing and Christopher J. Chiaverina, Light Science: Physics and the Visual Arts, Springer, New York, 1999, hardback, ISBN 0-387-98827-0
- Robert Greenler, Rainbows, Halos, and Glories, Elton-Wolf Publishing, 1999, hardback, ISBN 0-89716-926-3
- Polarized Light in Nature, G. P. Können, Translated by G. A. Beerling, Cambridge University Press, 1985, hardcover, ISBN 0-521-25862-6
- M.G.J. Minnaert, Light and Color in the Outdoors, ISBN 0-387-97935-2
- John Naylor "Out of the Blue: A 24-hour Skywatcher's Guide", CUP, 2002, ISBN 0-521-80925-8
- Abenteuer im Erdschatten (German).
- The Marine Observers' Log
External links