Unit 07 Vocabulary

1. Sine curve -- the waveform traced by simple harmonic motion.

2. Amplitude -- for a wave or a vibration, the maximum displacement on either side of equilibrium (midpoint) position.

3. Wavelength -- the distance between successive crests, troughs or identical parts of a wave.

4. Frequency -- for an oscillating body or a wave, the number of vibrations per second.

5. Hertz -- the MKS unit of frequency; equivalent to 1 oscillation per second.

6. Period -- the time in which an oscillation is completed; it is the reciprocal of the frequency.

7. Transverse wave -- a wave in which the medium vibrates perpendicularly to the direction in which the wave travels.

8. Crest -- the highest point in a transverse wave.

9. Trough -- the lowest point in a transverse wave.

10. Longitudinal wave -- a wave in which the medium oscillates parallel to the direction in which the wave travels.

11. Compression -- the region in a longitudinal wave with a higher than average density or pressure.

12. Rarefaction -- the region in a longitudinal wave with a lower than average density or pressure.

13. Wave speed -- the rate at which a wave travels.

14. Simple Harmonic Motion (SHM) -- any (repeated) periodic motion (back and forth) with a restoring force proportional to displacement.

15. Simple pendulum -- an object with a small mass suspended from a light wire or string; it oscillates due to the combined forces of gravitation and tension.

16. Restoring force -- any force that always acts to pull a system back toward equilibrium.

17. Elastic force -- force exerted by a material when it is stretched or compressed.

18. Oscillation -- a movement in one direction and then back in another direction around an equilibrium position.

19. Wave interference -- the phenomenon that occurs when two waves meet while traveling along the same medium.

20. Standing wave -- a stationary interference pattern formed in a medium when two sets of identical waves pass through the medium in opposite directions.

21. Doppler effect -- the shift in received frequency due to the motion of a vibrating source toward or away from a receiver.

22. Bow wave -- the V-shaped disturbance created by an object moving across a liquid surface at a speed greater than the wave speed.

23. Shock wave -- the cone-shaped disturbance created by an object moving at supersonic speed through a fluid.

24. Speed of sound -- the speed at which sound vibrations move through a particular medium; the speed of sound varies with the characteristics of the medium; in general, it is faster when the medium is more density and its particles are more rigidly held in place.

25. Pitch -- the highness or lowness of a tone; related to the wave frequency.

26. Sound intensity -- an objective measure of a sound's power, related to the square of its amplitude.

27. Loudness -- a somewhat subjective measure of the volume of a sound; related to the intensity; measured in decibels.

28. Refraction -- the bending of a wave caused by a difference in wave speeds.

29. Forced vibration -- when a vibrating object causes objects around it to vibrate with the same frequency.

30. Natural frequency -- the frequency at which an elastic object tends to vibrate when it is disturbed and the disturbing force is removed.

31. Resonance -- the response of a body when a forcing frequency matches its natural frequency.

32. Constructive interference -- the resulting increase in amplitude when the same parts of two different waves attempt to move through the same portion of the medium.

33. Destructive interference -- the resulting decrease in amplitude when the opposite parts of two different waves attempt to move through the same portion of the medium.

34. Beats -- a series of alternate reinforcements and cancellations produced by the interference of two waves of slightly different frequencies, heard as a throbbing effect in sound waves.

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