March 30, 2022
In this chapter of AS/A-level Physics, we will learn more about the stationary waves .
Introduction of Stationary Waves
Progressive waves reflected at a boundaryàstationary (standing) wave is the superposition of two progressive waves with the same frequency (wavelength), moving in opposite direction
Stationary waves form oscillating loops separated by nodes
In AS/A-level Physics, each particle vibrates at right angles to the string. Nodes where amplitude is zero. It can be classified into First harmonic, Second harmonic, Third harmonic.
First harmonic:
- Vibrating at lowest possible resonant frequency. It has one “loop” with a node at each end
Second harmonic:
- Twice the frequency of the first harmonic. There are two “loops” with a node in the middle and one at each end
Third harmonic:
- Triple the frequency of the first harmonic. It has 1 and a half wavelengths fit on the string
For examples:
- In AS/A-level Physics, microwaves reflected off a metal surface/plate set up a stationary wave à First nodes and anti-nodes.
- Powder can show stationary waves in a tube of air à Lycopodium powder laid along the bottom and the powder is shaken away from the antinodes but left undisturbed at the nodes.
This is the end of the topic!