Light beam
A light beam or beam of light is a directional projection of light energy radiating from a light source. Sunlight forms a light beam when filtered through media such as clouds, foliage, or windows. To artificially produce a light beam, a lamp and a parabolic reflector is used in many lighting devices such as stage [lighting instrument#Spotlights|spotlights], car headlights, PAR Cans, and LED housings. Light from certain types of laser has the smallest possible beam divergence.
Visible light beams
From the side, a beam of light is only visible if part of the light is scattered by objects: tiny particles like dust, water droplets, hail, snow, or smoke, or larger objects such as birds. If there are many objects in the light path, then it appears as a continuous beam, but if there are only a few objects, then the light is visible as a few individual bright points. In any case, this scattering of light from a beam, and the resultant visibility of a light beam from the side, is known as the Tyndall effect.Visibility from the side as side effect
- Flashlight, beam directed by hand
- Headlight, forward beam; the lamp is mounted in a vehicle, or on the forehead of a person, e.g. built into a helmet
- Lighthouse, beam sweeping around horizontally
- Searchlight, beam directed at something
Visibility from the side as purpose
For the purpose of visibility of light beams from the side, sometimes a haze machine or fog machine is used. The difference between the two is that the fog itself is also a visual effect.Image:Classical spectacular [laser effects.jpg|right|thumb|Laser beams used for visual effects during a musical performance]
Image:Light Amplification by [Stimulated Emission of Radiation.jpg|right|thumb|Laser beams with different wavelengths (405nm - 660nm).]
- Laser lighting display- Laser beams are often used for visual effects, often in combination with music.
- Searchlights are often used in advertising, for instance by automobile dealers; the beam of light is visible over a large area, and interested persons can find the dealer or store by following the beam to its source. This also used to be done for movie premieres; the waving searchlight beams are still to be seen as a design element in the logo of the 20th Century Fox movie studio.