Interference

When waves add up, or cancel

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Overlapping waves add together (superposition).
• In phase: constructive interference. Half a wavelength out of phase: destructive interference.
• Two close frequencies make beats at $|f_1 - f_2|$ per second.

Steps

1. Adding waves
2. Cancel out
3. Constructive and destructive
4. Two sources
5. Beats
6. Tuning a guitar
7. Two speakers