Superposition and standing waves.

Stationary waves.

What is superposition?

When the displacements of two waves are combined as they pass through each other.

The resultant displacement is the vector sum of each wave’s displacement.

What is constructive interference?

when 2 waves have displacement in the same direction

What is destructive interference?

When one wave has positive displacement and the other has negative displacement

• if the waves have equal but opposite displacements, total destructive interference occurs

How are stationary waves formed?

• 2 progressive waves with the same frequency, wavelength and amplitude travelling in opposite directions, superpose onto each other.

• Where the waves are in phase, they cause constructive interference resulting in an antinode. These are regions of maximum amplitude.

• Where the waves are in antiphase, they cause destructive interference, resulting in a node. These are regions of zero displacement.

What is the first harmonic?

The lowest frequency at which a stationary wave forms. A stationary wave with two nodes and an antinode. The distance between adjacent nodes (or antinodes) is half a wavelength for any harmonic.

Doubling the frequency of the first harmonic gives the second harmonic, tripling gives the third harmonic and so on…

What is a node on a stationary wave?

A region of zero displacement where there has been destructive interference

What is an antinode on a stationary wave?

A region of maximum amplitude (or displacement) where there has been constructive interference.

What is another name for a stationary wave?

Standing wave