Laser.
Light Amplified by the Stimulated Emission of Radiation. Lasers are devices which produce beams of coherent light - in other words, all of the light from the laser is of precisely the same wavelength (same colour - this is why lasers cannot produce white light) and vibrates in exactly the same phase. Normal light is not coherent - even light which has been filtered contains light of slightly different wavelengths and is not exactly in phase.
Finally, most laser light is also collimated - beams are parallel and thus do not exactly follow the inverse square law. Semiconductor lasers require collimating lenses, whereas non-semiconductor types (eg: ruby lasers, helium-neon lasers, etc.) contain parallel reflective mirrors which result in almost precisely collimated light. The fact that laser light is highly collimated is also why laser beams are so dangerous - the energy they contain is concentrated on a very small area and can instantly burn out the retina of an eye, causing immediate blindness.
Lasers are not commonly used in photographic applications, except for fairly specialized uses. For example, they’re often used for adjusting and calibrating lenses. They can also be used to trigger photographs remotely - a camera might be hooked up to a small laser and photodetector such that the camera takes a photo when a passing animal breaks the light beam. Finally, they can be used to create holographic images.
cf. coherent light, collimated light, holography, inverse square law, laser printer, light, wavelength.
Entry last updated 2002-04-18. Term 693 of 1487.
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