A light beam or beam of light is a directional projection of light energy radiating from a light source.

Sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...

forms a light beam (a

sunbeam A sunbeam, in meteorological optics, is a beam of sunlight that appears to radiate from the position of the Sun. Shining through openings in clouds or between other objects such as mountains and buildings, these beams of particle-scattered sunl ...

) 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 spotlights, car headlights, PAR Cans, and

LED A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...

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 (

mist Mist is a phenomenon caused by small droplets of water suspended in the cold air, usually by condensation. Physically, it is an example of a dispersion. It is most commonly seen where water vapor in warm, moist air meets sudden cooling, such a ...

fog Fog is a visible aerosol consisting of tiny water droplets or ice crystals suspended in the air at or near the Earth's surface. Reprint from Fog can be considered a type of low-lying cloud usually resembling stratus, and is heavily influ ...

, rain),

hail Hail is a form of solid precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. Ice pellets generally fal ...

, 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 A flashlight ( US, Canada) or torch ( UK, Australia) is a portable hand-held electric lamp. Formerly, the light source typically was a miniature incandescent light bulb, but these have been displaced by light-emitting diodes (LEDs) since the ...

(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 A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lenses and to serve as a beacon for navigational aid, for maritime pilots at sea or on inland waterways. Lighthouses mar ...

, 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 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 (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

premiere A première, also spelled premiere, is the debut (first public presentation) of a play, film, dance, or musical composition. A work will often have many premières: a world première (the first time it is shown anywhere in the world), its first ...

s; 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. (previously known as 20th Century Fox) is an American film production company headquartered at the Fox Studio Lot in the Century City area of Los Angeles. As of 2019, it serves as a film production arm of Walt Dis ...

movie studio A film studio (also known as movie studio or simply studio) is a major entertainment company or motion picture company that has its own privately owned studio facility or facilities that are used to make films, which is handled by the production ...

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 b ...

** Infrared Data Association (IrDA) standards **

Infrared remote control In electronics, a remote control (also known as a remote or clicker) is an electronic device used to operate another device from a distance, usually wirelessly. In consumer electronics, a remote control can be used to operate devices such as ...

Security alarms A security alarm is a system designed to detect intrusion, such as unauthorized entry, into a building or other areas such as a home or school. Security alarms used in residential, commercial, industrial, and military properties protect against ...

* Fibre optics * Laser pointer * Laser sight * List of applications for lasers

References

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External links