Light interference occurs when two light waves interact with each other. Light interference often creates beautiful patterns, such as those on the surface of the bubbles shown above. When light hits a soap bubble, one light ray is reflected by the outer layer of soap, while another light ray will travel through that layer and get reflected by the inner layer of soap. Since these waves have traveled slightly different differences, the waves are no longer perfectly synchronized; this interference results in iridescent patterns.
This chapter discussed the nature of interference and interference patterns, the diffraction of light waves, and the use of diffraction gratings. Regardless of the number of slits, light shining through small slits in a blocking object will create an interference pattern. In single slits, this pattern is a result of light diffraction around the back of each side of the slit, while double slits and diffraction gratings create interference due to light shining through each slit.