Lasers create a pencil-thin beam so intense it will punch a hole through steel, and so straight and narrow it can be aimed precisely at a mirror on the moon, 384,401km away. This ia a ghosted view, showing the electric discharge source and the tube containing a mix of helium and neon. Laser light Laser beams give a beam of coherent light in which all the peaks and troughs of the waves of light are perfectly in step. Inside a laser there is a tube containing a mixture of gases such as helium and neon and a liquid or a solid crystal such as ruby.
Chemical lasers use liquid hydrogen fluoride to make intense beams for weapons.
Projecting into the tube are two electric terminals which create an electric spark. The spark gives extra energy to the atoms of the lasing material and excites them into firing off photons - little bursts of light. The photons shoot off through the lasing material in all directions, hitting other atoms and making them fire off photons too. Soon there are billions of identical photons zooming around within the tube. Mirrors at either end, however, reflect photons moving straight up and down the tube so that they zoom back and forth again and again, gathering more photons as they go.