In: Physics
Why is a diffraction grating better than a two-slit setup for measuring wavelengths of light?
The double-slit experiment works by shooting parallel light of rays from the same soure which is a laser, at a pair of parallel openings in order to cause interference. The reason behind this is that when the light hits the slits, it is in the same phase, so you can consider each slit to be a source of same light. When the light hits a wall, depending on what phase each beam is in they will interfere either constructively, providing mxima, or destructively providing minima. These interference patterns are seen as a series of bright and dark lines. Using a diffraction grating providing more slits, which increases the interference between the beams.
By using more slits, you get more destructive interference. The maxima on the other hand becomes much brighter because of increased constructive interference. This effectively increases resolution of the experiment, making it easier to measure the distance between the consecutive maxima.