Optical phenomena

File:Moon 22 degree halo atherton ca.jpg

A 22° halo around the moon in Atherton, CA.

Optical phenomena are any observable events that result from the interaction of light and matter. See also list of optical topics and optics. A mirage 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 rainbow, 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 Morganas, are commonplace in favored locations.

Other phenomena are simply interesting aspects of optics, or optical effects. For instance, the colors generated by a prism are often shown in classrooms.

File:SunHaloOverGoldenBay4thFeb06.jpg

Sun halo at latitude 41 degrees south

A list of optical phenomena

Optical phenomena include those arising from the optical properties of the atmosphere; the rest of nature (other phenomena); of objects, whether natural or human-made (optical effects); and of our eyes (Entoptic phenomena). Also listed here are unexplained phenomena that could have an optical explanation and "optical illusions" for which optical explanations have been excluded.

There are many phenomena that result from either the particle or the wave 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 Sun observed during a solar eclipse. This demonstrates that space is curved, as the theory of relativity predicts.

Atmospheric optical phenomena

The Circumzenithal Arc over Grand Forks, ND

File:Belt of Venus over Paranal Observatory.jpg

Belt of Venus over Cerro Paranal.

• Afterglow
• Airglow
• Alexander's band, the dark region between the two bows of a double rainbow.
• Alpenglow
• Anticrepuscular rays
• Anthelion
• Auroral light (northern and southern lights, aurora borealis and aurora australis)
• Belt of Venus
• Circumzenithal arc
• Cloud iridescence
• Crepuscular rays
• Earth's shadow
• Earthquake lights
• Glories (also known as Brocken's Specter or Specter of the Brocken)
• Green flash
• Halos, of Sun or Moon, including sun dogs
• Heiligenschein or halo effect, partly caused by the opposition effect
• Light pillar
• Mirages (including Fata Morgana)
• Rainbows
• Shadow set
• Sun dogs
• Tyndall effect

Other optical phenomena

File:Double Green Flash.jpg

Green flash appears above the solar disc for a second or so. One such occurrence was taken from Cerro Paranal.

• Dichromatism
• Gegenschein
• Iridescence
• Opposition effect
• Sylvanshine
• Zodiacal light

Optical effects

• Asterism, star gems such as star sapphire or star ruby
• Aura, a phenomenon in which gas or dust surrounding an object luminesces or reflects light from the object
• Aventurescence, also called the Schiller effect, spangled gems such as aventurine quartz and sunstone
• Baily's beads, grains of sunlight visible in total solar eclipses.
• camera obscura
• Cathodoluminescence
• Caustics
• Chatoyancy, cat's eye gems such as chrysoberyl cat's eye or aquamarine cat's eye
• Chromatic polarization
• Diffraction, the apparent bending and spreading of light waves when they meet an obstruction
• Dispersion
• Double refraction or birefringence of calcite and other minerals
• Double-slit experiment
• Electroluminescence
• Evanescent wave
• Fluorescence, also called luminescence or photoluminescence
• Mie scattering (Why clouds are white)
• Metamerism as of alexandrite
• Moiré pattern
• Newton's rings
• Phosphorescence
• Pleochroism gems or crystals, which seem "many-colored"
• Polarized light-related phenomena such as double refraction, or Haidinger's brush
• Rayleigh scattering (Why the sky is blue, sunsets are red, and associated phenomena)
• Refraction
• Sonoluminescence
  • Shrimpoluminescence
• Synchrotron radiation
• The separation of light into colors by a prism
• Triboluminescence
• Thomson scattering
• Total internal reflection
• Twisted light
• Umov effect
• Zeeman effect
• The ability of light to travel through space or through a vacuum.

Entoptic phenomena

Main article: Entoptic phenomenon

• Diffraction of light through the eyelashes
• Haidinger's brush
• Monocular diplopia (or polyplopia) from reflections at boundaries between the various ocular media
• Phosphenes from stimulation other than by light (e.g., mechanical, electrical) of the rod cells and cones of the eye or of other neurons of the visual system
• Purkinje images.

Optical illusions

Main article: Optical illusion

• The unusually large size of the Moon as it rises and sets, the moon illusion
• The shape of the sky, the sky bowl

Unexplained phenomena

See also: Forteana, Will-o'-the-wisp, and Unidentified flying object

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 attractions that are not worthy of thorough investigation.

• Marfa lights
• Hessdalen lights
• Min Min lights
• Light of Saratoga
• Naga fireballs

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

• Atmospheric Optics Reference site
• SpaceW Site for reporting Aurora activity data
• Spaceweather.com Official NASA site with many photos
• Astronomy in New Zealand Many atmospheric optical effect photos and descriptionsbg:Оптично явление