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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
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/4936730/512064_798940.jpeg)
Second harmonic:
- Twice the frequency of the first harmonic. There are two “loops” with a node in the middle and one at each end
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/4936730/165787_944326.jpeg)
Third harmonic:
- Triple the frequency of the first harmonic. It has 1 and a half wavelengths fit on the string
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/4936730/708449_945616.jpeg)
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!
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_60/4936730/396957_128721.gif)