Optical phenomenon

An optical phenomenon is any observable event, such as a rainbow, which results from the interaction of light and matter. Some optical phenomena, such as the blueness of the sky or the redness of a sunset, are commonplace, while others such as the green ray are so rare as to seem mythical. Some, such as instances of fata Morgana, are commonplace only in certain locations. Optical phenomena illustrate and are explained by the principles of optics.

Some optical illusions can be explained as observations of unusual optical phenomena.

Optical phenomena include:

• Afterglow
• Airglow
• Alexander's Band, the dark region between the two bows of a double rainbow.
• Alpenglow
• Asterism, star gems such as starsapphire or star ruby.
• Auroral light (northern and southern lights, aurora borealis and aurora australis)
• The unusually large size and rich color of the Moon as it rises and sets
• The Camera obscura
• Chromatic polarization
• cathodoluminescence
• Diffraction, the apparent bending and spreading of light waves when they meet an obstruction.
• dispersion
• Double refraction
• The Double-slit experiment
• electroluminescence
• fluorescence, also called luminescence or photoluminescence.
• Gegenschein
• Glories
• the Green ray
• Halos, of Sun or Moon
• metamerism as of alexandrite
• pleochroism gems or crystals which seem many-colored
• Sun Dogs
• Rayleigh scattering (Why the sky is blue, sunsets are red, clouds are white, and associated phenomena)
• Synchrotron radiation
• The separation of light into colors by a prism
• triboluminescence
• The Zeeman effect
• Thomson scattering
• Total internal reflection
• The Umov effect
• Zodiacal light
• Polarized light related phenomena such as double refraction, or Haidinger's brush
• The ability of light to travel through space or through a vacuum.

There are many phenomena which 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 was of the bending of light from a star by the Sun during a solar eclipse. This demonstrated that light had mass (or did it show that space is curved?) See Theory of relativity.

Observations of some phenomena such as the photoelectric effect, 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, as they could not be easily explained by existing theory.

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 0897169263
• Polarized Light in Nature, G. P. Können, Translated by G. A. Beerling, Cambridge University Press, 1985, hardcover, ISBN 0-521-25862-6