Lasers - Powerful Beams of Light
Laser means “light amplification by stimulated emission of radiation”. A laser is an object that produces beams of light which can travel very long distances. Such beams are so powerful that they can cut through a diamond, the hardest material in the world.
The first lasers were developed in the 1950s by American and Russian scientists. However, the idea of creating beams of light that are very powerful had come up a century before. At that time lasers were purely science fiction, devised by writers like HG Wells. In his novel War of the Worlds, for example, he wrote about Martians who had a weapon called a heat ray.
Normal light consists of many wavelengths and colors. Laser light, in contrast, does not scatter but moves in the same direction. It produces light in a single color and wavelength. When electrons move from a lower level to a higher level around an atom they emit a photon, a particle of light. After that they tend to fall back to their original orbit.
In order to make a laser beam you need a tube with mirrors on both ends. In it there is an active medium, which can be a liquid, gas or a solid. An energy source produces the light that you need to excite the electrons. Photons reflect off the mirrors, they travel back and forth, stimulate other electrons and , thus, produce colored light .
Red light, for example, is produced when you heat up something. When you watch TV and see a colorful picture, it is actually phosphor atoms which release energy.
Uses of lasers
Lasers are used in many situations in different areas of life. They are used to record and store different kinds of information, for example music, videos or other data. They also act as instruments, when exact measurements are needed. Therefore you can find lasers in various medical instruments in hospitals, at home in DVD players or in the laser printers of offices. Lasers can also produce 3-D images called holograms.
Modern medicine uses lasers to destroy tumors in your body or to correct eyesight. Many surgeons perform operations with laser beams instead of knives. They can remove damaged tissue from your body without destroying the cells around it.
In the world of communication lasers are used in telephone signals and in optical cables. Lasers are also used in the bar code scanners of supermarkets, where they transmit information to a cash register.
The entertainment industry produces lines of colored light and makes special effects for stages and shows.
Industry uses the heat produced by lasers to cut holes in objects or to make material stronger. Intelligent weapons use laser-guided systems to pinpoint a target.
Because laser light can travel very long distances, astronomers use laser beams to measure the distance to the moon and other planets.
The police use a laser speed gun in traffic
- amplification = to make something stronger
- astronomer = person who studies the sky and the stars
- back and forth = here: from one mirror to the other and back again
- bar code scanner = an instrument that can read the code on products
- beam = line
- cash register = machine used in shops to add up amounts and keep money in
- century = a hundred years
- consist of = to be made up of
- correct = put right
- data = information
- destroy = kill
- develop = make, produce
- devise = create
- distance = space
- electron = a very small particle that moves around the center of an atom; it normally has a negative charge
- emission = release
- exact = correct, accurate, perfect
- excite = stimulate; to make something move
- eyesight = vision
- hologram = picture that does not look flat if you look at it from a different sides
- however = but
- in contrast = on the other hand
- instead of = in something’s place
- laser-guided = controlled by lasers
- liquid = material that is not gas or a solid, like water or milk; a fluid
- Martians = a made-up creature from the planet Mars
- mirror = piece of glass that you can see yourself in
- novel = a long written story in which characters are not real
- optical = to be seen
- orbit = to go around an object
- phosphor = yellowish chemical substance that starts to burn when it is in the air and shines in the dark
- pinpoint = find the exact location of something
- purely = only
- radiation = energy in the form of heat and light that is sent out as waves that you cannot see
- ray = a line of light or energy
- record = to write down information
- reflect = bounce, move
- release = set free
- remove = here: cut out
- scatter = to move in all directions
- scientist = a person who works in the laboratory and is trained in science
- solid = an object that has a fixed shape; not a gas or a liquid
- stage = place where a play or musical takes place
- stimulate = excite
- store = save
- surgeon = a doctor who performs operations
- target = goal
- tend to = something normally happens
- thus =therefore
- tissue = the material that forms cells
- transmit = send information from one place to another
- tube = round pipe made of metal, glass or other materials
- tumor = bad cells in your body that reproduce very quickly
- various = different
- wavelength = the distance between two waves of light or energy
- weapon = something you use to fight with , like a gun or a bomb