1. Interference of light waves Three slides

2. Constructive and Destructive Interference The graphic on the right shows two waves coming towards each other. The blue wave at the bottom shows the wave that forms when the top two waves meet. When does the new wave formed have the highest amplitude? When do the waves cancel each other out? Animation courtesy of Dr. Dan Russell, Kettering University

4. When two waves of identical wavelength are in phase, they form a new wave with an amplitude equal to the sum of their individual amplitudes (constructive interference). When two waves are of completely opposite phase, they either form a new wave of reduced amplitude (partial destructive interference) or cancel each other out (complete destructive interference). Encyclopædia Britannica, Inc.