1. Chapter 13
Waves and Sound

2. Vibrations & Waves
Wave: A vibration that moves through space and time.
Sound – the movement of vibrations of matter – through solids, liquid or gases - if there is no matter to vibrate, then there is no sound. Sound cannot travel through a vacuum.
Light – Vibration of electric & magnetic fields – vibration of pure energy. Light can travel through materials, but none is required.

4. sine curve Mathematical term for a wave is a:
(shaped like rolling hills and valleys)

5. Crests = high points of wave
Troughs = low points of wave
Midpoint or “home” position

6. Amplitude – distance from midpoint to crest or trough of the wave
Wavelength – distance from one crest to the next one
Frequency – how often a wave occurs

7. Period = --------------
Frequency (Hertz) or (Hz): 1 vibration per second is 1 Hz; 5 vibrations per second = 5Hz
Period – the time it takes for a complete vibration 1
Frequency =
period
Period =
frequency

8. Wave Speed
Energy is carried by waves not the material it’s moving through – speech and air
Example: when you talk the energy of your voice travels across the room at ~340 meters/second. Wave energy travels, not the air itself.

9. Wave Speed = frequency X wavelength
Example:
If a water wave vibrates up and down three times each second and the distance between wave crests is 2 m, what are (a) the wave’s frequency? (b) its wavelength? (c) its wave speed?
(a) 3 Hz; (b) 2 m; (c) 6 m/s

10. Wave Speed
v = f λ
V = wave speed
f = frequency
λ = wavelength

11. Open-Notebook Quiz
1. The mathematical term for a wave is a ______ ______.
2. T/F Sound can travel through a vacuum.
3. T/F Light does not need materials in order to exist.
4. ______ are the high points in a wave. ______ are the low points in the wave and the _______ position is the mid-point of a wave.
_______ tells you the distance from the mid-point of a wave to its trough or crest.
________ is the distance from one crest to the next one.
T/F Frequency tells you how often a wave occurs and is measured in Hertz (Hz).
What is the formula for figuring out the period of a wave, which is the time it takes for a complete vibration.