1. Introduction to Waves
Chapter 17

2. Characteristics of Waves
Waves are rhythmic disturbances that carry energy through matter or space.
Whatever the wave is traveling through is called the “medium.”
2 types of waves:
Transverse
Longitudinal

3. What type of wave does sound travel in?
Longitudinal: AKA: compression waves
Must travel through a medium
In space, there is NO MEDIUM (air) so there is NO SOUND!

4. What is a transverse wave?
Travel perpendicular to medium

5. Parts of a wave Crest: top of the wave Trough: bottom of wave
Amplitude: from resting position to top: height of wave = LOUDNESS
Wavelength: crest to crest or trough to trough (length of wave). Symbol: lamda:

6. Longitudinal waves

7. What is frequency?
Frequency is a term that refers to how many cycles can occur in one second.
As I’m sure you’ve guessed…in sound in controls the PITCH of the sound (low notes and high notes)
Frequency is measured in hertz (Hz)
How old are your ears?

8. Wave Velocity and Frequency
The higher the pitch of the note (higher the note played), the faster the frequency is.
Frequency = the number of wave crests that pass one place each second.

9. Speed of waves: VELOCITY
Wave velocity = how fast a wave moves.
Velocity = wavelength x frequency

10. Example:
The frequency of a wave is 40 Hz and its speed is 100 meters per second. What is the wavelength of this wave?

11. Solution!
v = Hz x
Re-arrange that formula!
= v ÷ Hz

12. End notes part 1

13. What is music?

14. Music to your ears
The sound waves produced to make music is repeating. Noise is more random.

15. Interference - Constructuve

16. Interference - Destructive

17. The Doppler Effect
A bug stationary on water is jiggling, causing circular wave fronts to spread out. The frequency of the disturbance is the same for observers at A and b.
If bug is moving, wavefronts arriving at B are closer together in time; the reverse is true for the observer at A.

18. More on the Doppler Effect
Approaching, the frequency is higher because the wavefronts are closer together in time. Departing, the frequency is lower.