1. Section 3
Behavior of Waves

2. Key Concepts How does reflection change a wave?
What causes the refraction of a wave when it enters a new medium?
What factors affect the amount of diffraction of a wave?
What are two types of interference?
What wavelengths will produce a standing wave?

3. Reflection
The bouncing back of a wave after it strikes a boundary that does not absorb all the wave’s energy
Angle of incidence = angle at which the wave hits the boundary
Angle of Reflection = angle at which the wave bounces off the boundary
Angle of Incidence = Angle of Reflection
Reflection does not change the speed or frequency of a wave, but the wave can be flipped upside down.

6. Refraction The bending of waves due to a change in speed.
Occurs because waves move at different speeds through different mediums.
When a wave enters a medium at an angle, refraction occurs because one side of the wave moves more slowly than the other side.

7. Refraction

8. Refraction

9. Diffraction The bending of waves around the edge of an obstacle
Diffraction is the result of a new series of waves being formed when the original waves strike an obstacle.
A wave diffracts more if its wavelength is large compared to the size of an opening or obstacle.

12. Interference
When two waves arrive in the same place at the same time, they interact
There are two types of interaction:
Constructive Interference – waves combine in such a way that the disturbance that results is greater than either wave alone
Destructive interference – waves combine in such a way that the disturbance that results is less than either wave alone
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15. Standing Waves A wave that does not appear to be moving
Two parts of a Standing Wave
Nodes: where destructive interference results in no energy displacement
Antinodes: where constructive interference causes maximum energy displacement
A standing wave forms only if half a wavelength or a multiple of half a wavelength fits exactly into the length of a vibrating cord.
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16. Reviewing Concepts 1. How is a wave changed by reflection?
2. What causes refraction when a wave enters a medium at an angle?
3. What determines how much a wave diffracts when it encounters an opening or an obstacle?
4. List the types of interference.
5. At what wavelengths can a standing wave form in an elastic cord?