Waves and Interference Transverse & Longitudinal Waves

Waves and Waves and InterferenceInterferenceWaves and Waves and

InterferenceInterference

Transverse & Longitudinal Transverse & Longitudinal WavesWaves

Transverse Waves• A person shakes the free end of a

rope up & down.

• The wave moves to the right.• The motion of the rope is at

RIGHT ANGLES to the direction in which the wave is moving.

• This is a transverse wave.– Eg: Strings in musical instruments,

– Waves in a stadium.

T

Longitudinal Waves• Sometimes the medium and the

wave move in the same direction (parallel).

• These are longitudinal waves.• Ex: Sound waves.

compressioncompression

rarefactionrarefaction

Identify the wave:Transverse wave – Spring is moved

up & down

Longitudinal Wave - Spring is moved

in and out

Interferences• Occur when 2 waves pass through each

other.• 2 types of interference:• 1) Constructive Inference:

2 Crests that pass through each other make a BIGGER wave.

2) Destructive Interference:2 Waves that pass through each

other make a SMALLER wave.

Interference

Constructive Interference

Destructive Interference

crest to crest adds to amplitude

crest to trough reduces amplitude

Lab on Waves• Move into groups of 4 ONLY.• DO NOT TANGLE THE SLINKIES.• DO NOT STRETCH the slinkies too

much.

DebriefPart I – Longitudinal Waves

• In which direction do the pieces of string move as the wave moves through the slinky?Part II – Transverse Waves

• In which direction do the pieces of string move as the wave moves through the slinky?

2. What will happen to the frequency, period and wavelength if you shake the spring faster?

• Frequency –• Period –• Wavelength –

Part III - Interference• Step 2 – Constructive Interference• Step 3 - Destructive Interference