LASERS

• Laser light is a bright artificial light. It creates an intense beam that can punch a hole in steel. A laser beam is so straight and narrow that it can hit a mirror on the Moon.
• The name 'LASER' stands for Light Amplification by Stimulated Emission of Radiation.
• Laser light is even brighter for its size than the Sun.
• Laser light is the only known 'coherent' source of light. This means the light waves are not only all the same wavelength (colour), but they are also perfectly in step.
• Inside a laser is a tube filled with gases, such as helium and neon, and a liquid or solid crystal such as ruby.
• Lasers work by bouncing photons (bursts of light) up and down the tube until they are all travelling together.
• Lasing begins when a spark excites atoms in the lasing material. The excited atoms emit photons. When the photons hit other atoms, they fire off photons too. Identical photons bounce backwards and forwards between mirrors at either end of the laser.
• Gas lasers such as argon lasers give a lower-powered beam. It is suitable for delicate work such as eye surgery.
• Chemical lasers use liquid hydrogen fluoride to make intense beams for weapons.
• Some lasers send out a continuous beam. Pulsed lasers send out a high-powered beam at regular intervals.