AP Physics 2 / Unit 14: Waves, Sound, and Physical Optics
14.6 Wave Interference and Standing Waves
Notes
- Superposition: overlapping waves add. Constructive (in phase) or destructive (out of phase).
- Standing waves have nodes and antinodes. String fixed at both ends: $\displaystyle \lambda_n=\frac{2L}{n}$.
- Open pipe: $\displaystyle \lambda_n=\frac{2L}{n}$; closed pipe: odd harmonics, $\displaystyle \lambda_n=\frac{4L}{n}$.
Practice
Two pulses of +3 cm and −3 cm overlap. The result:
Destructive.
The fundamental wavelength on a 2 m string fixed at both ends:
$2L$.
A node is a point of:
Never moves.
Ready for more? Take the Unit 14 test.