Wave Behavior

1
Wave Behavior

• Reflection
• Refraction
• Diffraction
• Interference

2
A. Reflection

• Wave bounces off a surface it cannot pass through
• Usually a hard surface like a mirror, water, the
  wall, etc.
• Wave speed does not change when it reflects.
• Direction may change (it may flip upside down)

3
A. Reflection

• Tied End Reflection

• Loose End Reflection

4
A. Reflection

• Soft surfaces absorb waves
• i.e. Yelling into a pillow the soft pillow
  absorbs the sound.
• When a wave loses energy and dies out, it is
  called damping.
• A cars shocks damp the wave motion of a car
  after it goes over a bump in the road.

5
A. Reflection

• Echolocation
• Many animals use the echos (reflections) of the
  sound waves they produce to locate an object or
  prey.
• Humans use echolocation in
• Sonar (Submarines)
• Radar (Airports using light waves)
• Sonograms (Ultrasound for unborn babies)

6
B. Refraction

• Wave bends as it enters a new medium at an angle.
• The waves speed changes when it enters a new
  material.
• Two sides of wave travel at different speeds.
• This causes the wave to change direction.

7
B. Refraction

• The lawnmower slows down as it travels from the
  sidewalk to the grass, which causes its path to
  bend.

8
B. Refraction

• Prisms refract light to separate its colors into
  a rainbow.
• Why objects submerged in water look bent

9
C. Diffraction

• Wave bends around a corner or spreads out through
  an opening.

10
C. Diffraction

• Wavelength must be large compared to obstacle.
• The larger the wavelength in comparison to the
  obstacle, the greater the diffraction.

11
D. Interference

• Two or more waves combine together when they
  overlap.

12
D. Interference

• Constructive Interference
• Waves add together to make a new wave with larger
  amplitude.
• Waves are in phase (overlap crest to crest or
  trough to trough)

13
D. Interference

• Examples
• Pushing a kid on a swing to give him energy when
  he is traveling away from you.
• Two singers on the same note cause a louder sound
  -- constructive interference

14
D. Interference

• Destructive Interference
• Waves subtract to make a new wave with smaller
  amplitude.
• Waves are out of phase (overlap crest to trough
  or somewhere in between)

15
D. Interference

• Example
• Modern headphones and cars have noise canceling
  technology. They create out of phase waves that
  cancel each other out.