Unit 11 Review Waves and Sound
1. Waves transfer energy, not matter.
2. Amplitude is the maximum movement from rest i.e. it is the amount of energy carried by a
wave. It is proportional to energy. Wavelength is the distance between consecutive crests or
troughs. Period is the time for one complete cycle or wave. Frequency is the number of
complete waves per unit time.
3. Wave speed depends on the tension and density of the medium. The more tension= the more
speed. The more dense= less speed. Amplitude and wavelength does not affect speed.
4. Velocity=frequency(wavelength) or velocity=displacement/time
5. Examples of transverse waves are rope and light. They make an up and down motion.
Longitudinal wave example is sound. They make a back and forth motion. A compression is the
crest of a longitudinal wave and a rarefaction is a trough of a longitudinal wave.
6. EM are electromagnetic waves like light and radio, they do not require a medium. Mechanical
waves are like sound and water waves and they require an elastic medium like air.
7. A standing wave is a wave that does not appear to be moving. They are produced by the
interference of 2 periodic waves of the same amplitude and wavelength traveling in opposite
directions. The frequency that they occur at is called the resonant frequency.
8. Constructive interference is when waves add together (crests meet crests and trough meets
trough). Destructive interference is when the waves subtract (crests meet trough).
9. A fixed end reflection is where a reflected wave inverses and moves in the opposite direction. A
free end reflection is where a reflected wave does not inverse but still moves in the opposite
direction.
10. You can change the density of the medium such as going from solid to liquid or gas which is
connected to temperature. You could also change the tension of the medium itself.
11. Sound is a longitudinal mechanical wave that requires a medium. It has speed, intensity,
frequency, and harmonic content.
12. No sound is possible in space because space is a vacuum and therefore doesn’t have air to act as
a medium for sound.
13. Pitch is the frequency of a sound wave, loudness is the intensity and tone is the harmonic
content.
14. A fundamental is the lowest pitch that produces 1 antinode. Resonance also occurs at the
harmonics.
15. See worksheets
16. Doppler Effect is a change in frequency produced by the relative motion of the sound and the
listener.
17. Ultrasonic- above 20,000 Hz (the extent of human hearing). Infrasonic- below 20 HZ (the lowest
of human hearing). Subsonic- speeds below the speed of sound. Supersonic- speeds above the
speed of sound.
18. Decibels are levels of human hearing. 0 dB – threshold of hearing. 120 dB- threshold of pain