Waves and Interference

1
Waves and Interference

• Transverse Longitudinal Waves

2
Transverse Waves
N

• 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
3
Longitudinal Waves
N

• Sometimes the medium and the wave move in the
  same direction (parallel).
• These are longitudinal waves.
• Ex Sound waves.

compression
rarefaction
4
Identify the wave

• Transverse wave
• Spring is moved up down
• Longitudinal Wave
• - Spring is moved in and out

5
Interferences
N

• 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.

6
Interference
Constructive Interference
Destructive Interference
crest to crest adds to amplitude
crest to trough reduces amplitude
7
Lab on Waves

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

8
Debrief

• Part 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

9
Part III - Interference

• Step 2 Constructive Interference
• Step 3 - Destructive Interference