What happens when two wave pulses collide?

• Interference– Two waves “collide,” but pass through each

other undamaged– Superposition Principle: when waves interfere

with each other, the resulting wave is the sum of their amplitude at each point.

Destructive Interference

Constructive Interference

Constructive Interference

• crests aligned with crests

• waves are “out of phase”

Destructive Interference

• crests aligned with troughs

• waves are “out of phase”

• Interference– Add the amplitudes of the waves• Above axis is positive, below is negative

– The result is the superposition of the waves– Constructive wave gets bigger– Destructive wave gets smaller

What if we send a bunch of pulses down the spring and let them reflect back? How will they interfere with one another?

Standing waves

Animation

Parts of a Wave

2 4 6 x(m)

3

-3y(m)

Crest/antinode

Trough/antinode

node

Wave Parameters

3

-3

2 4 6 x(m)

y(m)

amplitude

wavelength

wavelength

• You can make a standing wave on a spring. – Figure out how to make different standing

waves.– What would a graph of wavelength vs. # of

antinodes look like?– Collect the data to make this graph.

Wav

elen

gth

# of antinodes