If you hold a magnifying glass so that it concentrates a beam of sunlight on to a piece of paper – and hold it steady for a few minutes – the paper will start to smoke and then catch fire. That is one way of cutting through things with light. But paper is rather different from steel. Yet laser beams can cut through steel faster than you can burn paper with a magnifying glass. The secret is that they use a different sort of light.
Light waves usually overlap as they pass through the air. When this happens, the energy in one wave cancels out the energy in another. In a laser the light waves work together. Therefore all the energy can be channeled into a very narrow, powerful beam of light. This is powerful enough to cut through steel, or send a pencil-thin beam of light over great distances on earth and far out into space. In America, military scientists are trying to develop lasers that can even knowck out nuclear missiles.
Picture Credit : Google
