Red Laser Again

why the laser beam iss red?
- ahmed (age 12)
seoul, korea

Ahmed-If you’ve ever looked at light through a prism, or just looked up at a rainbow, you know that most light is made up of a number of different colors. An ordinary light bulb looks white, but it’s really made up of all the different colors of the rainbow. If you want to, you can make different colored lights by putting a filter over a regular light bulb that only lets certain colors through, but the light bulb is still making all the colors. It’s just that you only see certain ones.The way a laser works different from this, though. Unlike an ordinary bulb, which creates all the different colors, a laser is designed in such a way that it produces only a single wavelength, or color, of light. It also makes the light perfectly focused into a beam. Physicists say the light is "coherent."By the way, not all lasers are red. They make lasers in other colors, too, depending on the type of gas inside. The helium-neon laser, which produces the red light you are familiar with, is the most common one, though.MG

(published on 10/22/2007)