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| Sunday, 1 May 2005 |
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Junior Observer |  |
| News Business Features Editorial
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Laser - A beam of light
Lasers show up in an amazing range of products and technologies. We can find them in everything from CD players to dental drills to high-speed metal cutting machines to measuring systems. But what is a laser? And what makes a laser beam different from the beam of a flashlight? "Laser" is an acronym for Light Amplification by Stimulated Emission of Radiation, which describes how a laser works. A laser controls the way that energized atoms release photons. An atom absorbs energy in the form of heat, light, or electricity. Electrons may move from a lower-energy orbit to a higher-energy orbit. This is a simplified view of things, but it actually reflects the idea of how atoms work in terms of lasers. Once an electron moves to a higher-energy orbit, it eventually wants to return to the ground state. When it does, it releases its energy as a photon-a particle of light. We see atoms releasing energy as photons all the time. For example, the heating element in a toaster turning bright red, is caused by atoms, excited by heat, releasing red photons. When we see a picture on the TV screen, what we are seeing is phosphor atoms, excited by high-speed electrons, emitting different colours of light. Anything that produces light-fluorescent lights, gas lanterns, incandescent bulbs-does go through the action of electrons changing orbits and releasing photons. Although there are many types of lasers, all have certain essential features. In a laser, the lasing medium is "pumped" to get the atoms into an excited state. Typically, very intense flashes of light or electrical discharges pump the lasing medium and create a large collection of excited-state atoms (atoms with higher-energy electrons). It is necessary to have a large collection of atoms in the excited state for the laser to work efficiently. In general, the atoms are excited to a level that is two or three levels above the ground state. This increases the degree of population inversion. The population inversion is the number of atoms in the excited state versus the number in ground state. Once the lasing medium is pumped, it contains a collection of atoms with some electrons sitting in excited levels. The excited electrons have energies greater than the more relaxed electrons. Just as the electron absorbed some amount of energy to reach this excited level, it can also release this energy. The electron can simply relax, and in turn rid itself of some energy. This emitted energy comes in the form of photons (light energy). The photon emitted has a very specific wavelength (colour) that depends on the state of the electron's energy when the photon is released. Two identical atoms with electrons in identical states will release photons with identical wavelengths. Look out for more about lasers later. **** The basics of an atom There are only about 100 different kinds of atoms in the entire universe. Everything we see is made up of these 100 atoms in an unlimited number of combinations. How these atoms are arranged and bonded together determines whether the atoms make up a cup of water, a piece of metal, or the fizz that comes out of your soda can! Atoms are constantly in motion. They continuously vibrate, move and rotate. Even the atoms that make up the chairs that we sit in are moving around. Solids are actually in motion! Atoms can be in different states of excitation. In other words, they can have different energies. If we apply a lot of energy to an atom, it can leave what is called the ground-state energy level and go to an excited level. The level of excitation depends on the amount of energy that is applied to the atom via heat, light, or electricity. |
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| Politics | Produced by Lake House |
We have heard about lasers. The first thing that comes to our minds
when we hear the word laser, is bright coloured laser beams. 
