Diffraction grating consists of a large number of closely spaced parallel slits

• Diffraction gratings produce interference patterns that are similar to those from a double slit, but the maxima are far narrower and more intense
• The angle $\theta _m$ for the $m$th-order maximum of a diffraction grating with slit spacing $w$ and light wavelength $\lambda$ is given by $m \lambda = w \sin \theta _m = \triangle x$
  • Gives the constructive points for the interference pattern
• Colours seen in a CD or DVD result from interference similar to the interference of light from a diffraction grating