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Light beam
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<h2 id="visible-light-beams">Visible light beams</h2> <p>From the side, a beam of light is only visible if part of the light is scattered by objects: tiny particles like <a href="/facts/Dust/vaNKP8wk">dust</a>, water droplets (<a href="/facts/Mist/BywtmoJd">mist</a>, <a href="/facts/Fog/mrIdyIc7">fog</a>, <a href="/facts/Rain/MLqcQEyx">rain</a>), <a href="/facts/Hail/8sVew1sN">hail</a>, <a href="/facts/Snow/HEFKcgIB">snow</a>, or <a href="/facts/Smoke/KRJaumoC">smoke</a>, or larger objects such as <a href="/facts/Bird/RJF6zwLP">birds</a>. 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 <a href="/facts/Tyndall_effect/QJ9I8yeI">Tyndall effect</a>. </p> <h3>Visibility from the side as side effect</h3> <ul><li><a href="/facts/Flashlight/WFx32GbI">Flashlight</a> (UK 'Torch'), beam directed by hand</li> <li><a href="/facts/Headlight/7fg0kjKa">Headlight</a>, forward beam; the lamp is mounted in a vehicle, or on the forehead of a person, e.g. built into a <a href="/facts/Helmet/jDxsnLKp">helmet</a></li> <li><a href="/facts/Lighthouse/HAwW4RFW">Lighthouse</a>, beam sweeping around horizontally</li> <li><a href="/facts/Searchlight/Gprkyush">Searchlight</a>, beam directed at something</li></ul> <h3>Visibility from the side as purpose</h3> <p>For the purpose of visibility of light beams from the side, sometimes a <a href="/facts/Haze_machine/nwJq7h59">haze machine</a> or <a href="/facts/Fog_machine/I9XTvm0Q">fog machine</a> is used. The difference between the two is that the fog itself is also a <a href="/facts/Visual_effect/AdoEkAWU">visual effect</a>. </p> <ul><li><a href="/facts/Laser_lighting_display/YkI9btKB">Laser lighting display</a>- <a href="/facts/Laser/jk6PTvvT">Laser</a> beams are often used for visual effects, often in combination with music.</li> <li>Searchlights are often used in <a href="/facts/Advertising/Hgz271hW">advertising</a>, for instance by <a href="/facts/Automobile/I1IsH8IK">automobile</a> 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 <a href="/facts/Film/wM3b9Kk3">movie</a> <a href="/facts/Premiere/cRngvJPe">premieres</a>; the waving searchlight beams are still to be seen as a design element in the logo of the <a href="/facts/20th_Century_Fox/vd5eeD3S">20th Century Fox</a> <a href="/facts/Movie_studio/aG1MBQRl">movie studio</a>.</li></ul> <h2 id="other-applications">Other applications</h2> <ul><li><a href="/facts/Optical_communication/gshoNBto">Optical communication</a> <ul><li><a href="/facts/Infrared_Data_Association/qf8bwPDD">Infrared Data Association</a> (IrDA) standards</li> <li><a href="/facts/Infrared_remote_control/A9zmkgIV">Infrared remote control</a></li></ul></li> <li><a href="/facts/Security_alarm/btzrpRr9">Security alarms</a></li> <li><a href="/facts/Fibre_optics/5ruuIFbj">Fibre optics</a></li> <li><a href="/facts/Laser_pointer/o6cgsoKa">Laser pointer</a></li> <li><a href="/facts/Laser_sight/SaP0CbMF">Laser sight</a></li> <li><a href="/facts/List_of_applications_for_lasers/SaP0CbMF">List of applications for lasers</a></li></ul> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Beam_diameter/rxCGx8q8">Beam diameter</a></li> <li><a href="/facts/Collimated_beam/lhd2hhPt">Collimated beam</a></li> <li><a href="/facts/Crepuscular_rays/vvq2hC9e">Crepuscular rays</a></li> <li><a href="/facts/Light_pillar/6PmLXfvN">Light pillar</a>, atmospheric optical phenomena</li> <li><a href="/facts/Pencil_beam/wQtPHxsa">Pencil beam</a></li> <li><a href="/facts/Ray_(optics)/PgUEC7Sm">Ray (optics)</a></li> <li><a href="/facts/Relativistic_beaming/oYA5XSjj">Relativistic beaming</a></li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="http://vega.org.uk/video/programme/164">A short video showing how you can put sound on a light beam and transmit it by the Vega Science Trust</a></li></ul>