A light beam or beam of light is a directional projection of

light Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

energy radiating from a light source.

Sunlight Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible spectrum, visible light perceptible to the human eye as well as invisible infrare ...

forms a light beam (a sunbeam) 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 Lighting or illumination is the deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural illumination by capturing daylight. ...

devices such as spotlights, car headlights, PAR Cans, and LED housings. Light from certain types of

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...

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 ( mist, fog,

rain Rain is a form of precipitation where water drop (liquid), droplets that have condensation, condensed from Water vapor#In Earth's atmosphere, atmospheric water vapor fall under gravity. Rain is a major component of the water cycle and is res ...

), hail,

snow Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water througho ...

, or smoke, or larger objects such as

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

s. 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 (UK 'Torch'), 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. * Laser lighting display-

Laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...

beams are often used for visual effects, often in combination with music. * Searchlights are often used in

advertising Advertising is the practice and techniques employed to bring attention to a Product (business), product or Service (economics), service. Advertising aims to present a product or service in terms of utility, advantages, and qualities of int ...

, for instance by

automobile A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...

dealers; the beam of light is visible over a large area, and (at least in theory) 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 20th Century Studios, Inc., formerly 20th Century Fox, is an American film studio, film production and Film distributor, distribution company owned by the Walt Disney Studios (division), Walt Disney Studios, the film studios division of the ...

movie studio.

Other applications

Optical communication Optical communication, also known as optical telecommunication, is communication at a distance using light to carry information. It can be performed visually or by using electronic devices. The earliest basic forms of optical communication date ...

** Infrared Data Association (IrDA) standards ** Infrared remote control * Security alarms * Fibre optics *

Laser pointer A laser pointer or laser pen is a (typically battery-powered) handheld device that uses a laser diode to emit a narrow low-power visible laser beam (i.e. Coherence (physics), coherent light) to highlight something of interest with a small brigh ...

* Laser sight * List of applications for lasers

References

{{reflist

External links