Stationary Waves

This lesson covers: 

1. Formation and characteristics of stationary waves
2. Stationary waves in strings and their properties
3. The role of stationary waves in musical instruments
4. Demonstrating stationary waves with microwaves
5. Calculating the speed of sound using stationary waves

What are stationary waves?

Stationary waves, or standing waves, appear motionless and are formed through the principle of superposition.

A stationary wave is formed by the superposition of two waves with the same wavelength, moving in opposite directions.

Their superposition results in points of constructive and destructive interference.

• Nodes - Points of destructive interference where the two waves cancel each other out, resulting in no movement or zero amplitude.
• Antinodes - Points of constructive interference where the waves reinforce each other, creating points of maximum movement or amplitude.

Unlike progressive waves, stationary waves don’t transfer energy; the energy vibrates within the medium, oscillating between the wave's boundaries.

Stationary waves in vibrating strings

The lowest possible observable standing wave is known s the fundamental mode or first harmonic. 

For the first harmonic on a string, an antinode forms at the centre of the sting with a node at each end. The length of string is equal to 21​λ .