Diffraction gratings are commonly used in monochromators, spectrometers, lasers, wavelength division multiplexing devices, optical pulse compression devices, and many other optical instruments. CDs and DVDs are good, easily observable examples of diffraction gratings.

What is a real life example of diffraction?

The effects of diffraction can be regularly seen in everyday life. The most colorful examples of diffraction are those involving light; for example, the closely spaced tracks on a CD or DVD act as a diffraction grating to form the familiar rainbow pattern we see when looking at a disk.

Why are diffraction gratings useful?

The diffraction grating is an immensely useful tool for the separation of the spectral lines associated with atomic transitions. It acts as a "super prism", separating the different colors of light much more than the dispersion effect in a prism.