Young's Double Slit Experiment
Light is sent through two vertical slits and is diffracted into a pattern of vertical lines spread out horizontally. Without diffraction and interference, the light would simply make two lines on the screen.
Source
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"OpenStax College, Young’s Double Slit Experiment. January 11, 2013."
http://cnx.org/content/m42508/latest/
OpenStax CNX
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