How do lasers work

A.� Lasers basically amplify light created by over excited atoms.

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Atoms are always excited and moving, but once they have become more excited they want to get rid of their excess energy and return to their previous state. They do this by releasing energy in the form of photons, or light particles.

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This is where the laser comes in. The laser, which stands for Light Amplification by Stimulated Emission of Radiation, controls the way the over excited atoms release photons. Excited atoms emit photons in a particular way, with the same wavelength (colour) and path and atoms excited to the same degree will release identical photons.

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But that isn't all. The released photon can make another excited atom release a photon with the same wavelength and path as itself, effectively duplicating itself. By using mirrors a laser can multiply this duplicating effect even further and so amplify light. The mirrors send the photons back and forth, releasing photons as they do so.

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Q.� Where do atoms get this extra energy

A.� Atoms are always moving, even the ones that make up the computer monitor you're looking at, but they have different levels of excitement. The extent to which an atom is excited is dependent on how much energy it receives, from a heat or light or electrical source.

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Q.� Is laser light the same as normal light

A.� No, laser light is made up of lots of duplicated photons, all having identical wavelengths and identical paths. However normal light has different wavelengths, and so colours, and paths.

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Q.� Are normal lasers harmful in anyway

A.� Yes, they can be. If you look at a laser light your eye interprets the beam as if it were coming from a distant object and so sees it as very small. The result is that your eye concentrates the laser light onto a tiny spot at the back of your eye, this high concentration of light burns the cells it lands on, in a similar way to how a magnifying glass concentrates sunlight onto combustible material to make fire.

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Q.� How do lasers used for things like disco lights differ from those used in surgery

A.� Lasers can be dangerous if misused, however they are also very effective for surgical procedures. Laser light is similar to normal light in that it can only travel so far into a substance until that substance absorbs it. This property means that lasers can be used to make a precise incision into human organs and flesh without the danger that the beam could travel too far and damage something.

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Surgical lasers wavelengths are set so that the light is absorbed before it gets to anything that it can damage. The only danger would be if a surgeon paused for a sufficiently long time before moving the laser along.

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Puzzled about how the same thing can do many different things Click here to see if The AnswerBank can help clarify things.

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by Lisa Cardy