Diffraction Grating
An excellent instrument to measure the wavelength of light is the diffraction grating. Diffraction
gratings can utilize both reflection (light reflects off the surface) or transmission (light passes
through). In either case the grating is equivalent to a large number of narrow parallel slits. The
transmission grating you will be using is a film placed on a glass backing. In order to understand
how a grating works, we recall1
the double slit experiment of Thomas Young: If one shines
monochromatic light with a wavelength λ on two very narrow slits that are a distance d apart
(see Figure 11.1), constructive interference will result at an angle θ at which