1. Waves Interactions
Principles of Physics

2. Boundary Where 2 media meet Where wave conditions change
Reflection, transmission, or both can occur

3. Waves at Boundaries
A wave travels from one medium to another (i.e. air into water)
Waves enter the new medium upright
How much energy is transmitted into the new medium depends on how different the media are.
The greater the difference in the media the less transmission
More of the energy is reflected (returns to the original medium)

4. Free/Open/Loose Boundary
Boundary that can move
Boundary moves in response to the wave
When wave travels from:
More dense to less dense
Wave remains upright upon reflection
Less dense to more dense
Wave flips upon reflection

5. Waves at Boundaries
When the wave goes from low density to high density the reflected wave is flipped (In this case it would return on the bottom)

6. Waves at Boundaries

7. Fixed Boundary Boundary that does not move Most energy is reflected
Wave flips upon reflection (crest becomes a trough)
Boundary Conditions

8. Absorption In the real world
some of the energy is absorbed by the medium in the form of heat (usually as a result of friction)
Some of the wave amplitude is lost as a result

9. Interference
-when the particles of a medium are affected by multiple waves at the same time -the vibration of each particle is the combination of the vibration that would occur as a result of each individual wave

10. Types of Interference
Constructive Interference: When multiple waves add up to create a larger amplitude

11. Types of Interference
Destructive Interference: When multiple waves add up to create a smaller amplitude

12. Interference
Constructive Interference Destructive Interference

13. Standing Waves occur when a wave is confined between two boundaries
Wave is reflected back and forth
The medium appears to be reflecting back and forth vertically
As the frequency changes the standing wave pattern changes
low frequency, long wavelength
high frequency, short wavelength

14. Standing Waves
Standing Waves applet

15. Standing Waves Interference occurs between the wave and its reflection
Where destructive interference occurs, nodes form
Node – particle remains at equilibrium
Where maximum constructive interference occurs, antinodes form
Antinode – particle is farthest from equilibrium

16. Diffraction “Bending” of waves around a boundary no change in medium
When a straight wave front hits a boundary the edges appear curved

17. Diffraction
The amount of bending that is noticeable depends on the wavelength and the size of the opening Wavelength ≥ slit size → more bending Wavelength < slit size → less bending

18. Diffraction and Interference
When there are multiple openings the diffracted waves will overlap and interfere
Constructive interference occurs where crests happen at the same time and place (where lines overlap on the diagram)
Destructive interference occurs where a crest and a trough happen at the same time and place (where lines overlap spaces on the diagram)

19. Diffraction and Interference
Where constructive interference occurs an increase in amplitude occurs (brighter area on diagram)
Wave form is magnified
Where destructive interference occurs a decrease in amplitude occurs (grey areas on diagram)
Wave form is cancelled out

20. What Depends on What Frequency: depends on source
Amplitude: depends on energy
Speed: depends on medium