A laser is a device that produces a very intense beam of light with properties that make it an essential piece of equipment across the whole spectrum of science.

Normal "white" light is a mixture of different wavelengths, each wavelength associated with a specific frequency and energy. This is why white light separates into a "rainbow" when it is beamed through a prism. Each color in the rainbow is a different wavelength of light, with short wavelength blue light at the energetic end of the spectrum and long wavelength red light at the low-energy end. Lasers are different because they produce light of only certain wavelengths, all of it traveling in the same direction. The light is also coherent , which means all the peaks and troughs of the different waveforms match up peak to peak and trough to trough. They are like soldiers that are not only marching...