1. 14.2 Wave Properties

2. Mechanical Waves Waves that require a medium
Sound, water, in air, on a Slinky
These waves are governed by Newton’s laws

3. Wave pulse a single bump or disturbance that travels through a medium
Periodic Wave a wave that moves up and down at the same rate

4. transverse wave longitudinal wave
a wave in which the particles of the medium move perpendicular to the direction of the energy
longitudinal wave
a wave in which the particles of the medium move parallel to the direction of the energy

5. surface wave
a wave where the particles of the medium move both parallel and perpendicular to the direction of the energy

6. Amplitude
The maximum displacement from rest position
more amplitude will take more energy

7. crest-highest point of a wave
trough-lowest point of a wave

8. Measuring a Wave Wavelength, l, Measured in m, cm, mm, nm
The distance from crest to crest or trough to trough

9. Phase
Any two points on a wave that are at least a wavelength apart are in phase.
Points that move opposite are 180o out of phase
Points can be any where from 0o to 180o out of phase

10. Period (T) measured in seconds(s)
the time for one cycle
frequency (f) measured in Hertz (Hz)
the number of cycles per second
or (reciprocals)

11. Speed or Velocity
Speed (v) measured in m/s
The speed of the wave
v = lf
v = d/t

12. Remember
Amplitude of a mechanical wave determines the amount of energy
The medium determines the speed of a wave

13. 14.3 Wave Behavior
Two particles cannot be in the same place at the same time. But waves can be. Waves can transfer two different energies through the same space and the same time.

14. Incident wave is the original wave from the source of disturbance
Reflected wave is the wave that bounces off of a boundary

15. Superposition of Waves
Principle of superposition
the displacement of a medium caused by two or more waves is the algebraic sum of the displacements caused by the individual waves
Interference is the result of superposition

16. Constructive Interference
When the displacement of the waves are in the same direction.
The resultant wave amplitude is larger than any individual wave

17. Destructive Interference
Complete destructive interference would be the exact amplitude, but in opposite direction, wavelength and speed
Results would be no transfer of energy
Destructive interference is not always complete

18. Standing Wave Node Antinode point of a wave that is not moving
the point of maximum displacement

19. Interference of two waves traveling in opposite direction with the exact same wavelength and opposite amplitudes
Energy reflected back and forth and is “standing” in the wave

20. Waves in Two Dimensions
Normal
line drawn perpendicular to the barrier
angle of incidence
the angle between the incidence ray and the normal

21. Angle of Reflection Law of Reflection
the angle between the reflected ray and the normal
Law of Reflection
the angle of incidence equals the angle of reflection

22. Refraction of Waves
The type of media determines the speed and the wavelength
The frequency remains unchanged when the wave moves from one medium into another

23. v=fl
If the medium causes the wave to slow down and frequency doesn’t change what happens to the wavelength?

24. If the medium causes the wave to speed up what happens to the wavelength?
If the waves go from one medium into another at an angle to the two mediums then there is a bending of the wave.

25. This bending is called refraction.
What happens to the angle of refraction if the wave speed increases? Decreases?