Theoretical Constructive and Destructive Wave Interference
The amplitudes of waves add together. (a) Pure constructive interference is obtained when identical waves are in phase. (b) Pure destructive interference occurs when identical waves are exactly out of phase (shifted by half a wavelength).
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"OpenStax College, Young’s Double Slit Experiment. January 11, 2013."
http://cnx.org/content/m42508/latest/
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