1. Wave Properties

2. Types of Waves Mechanical waves
Water waves, sound waves, waves that travel along a spring or rope
Requires a material medium
Newton’s laws govern the motion of mechanical waves

3. Types of Waves Electromagnetic waves Light waves, radio waves, X-rays
No medium is needed
All travel through space at the speed of light 2.99 x 108m/s
Details cannot be observed directly
Will use the easily observed mechanical waves as models for the behavior of EM waves

5. Types of Waves Matter waves
Electrons and other particles show the wave-like behavior under certain conditions
Quantum mechanics are needed to describe these properties

6. Mechanical Waves Three different types
Each type disturbs the media in a different way
Transverse wave
Longitudinal wave
Surface wave

7. Transverse Wave
Causes the medium to vibrate perpendicularly to the direction of motion of the wave
Example: waves in piano and guitar strings

8. Longitudinal Wave
Causes the particles of a medium to move parallel to the direction of the wave
Example: sound wave
Fluids, liquids, gases, or plasma usually only longitudinal

10. Surface Wave Mixture of transverse and longitudinal waves
Energy of water waves usually comes from storms far away

11. How are waves produced?
Wave pulse: single disturbance that travels through a medium
A given point was at rest before the pulse reached it; it returned to rest after the pulse passed
Created by sudden jerking of the rope to one side and returning to center
Traveling wave
Created by moving rope side to side in a regular manner
A source that is vibrating with simple harmonic motion will produce a continuous travelling wave

12. Measures of a Wave
Period (T): shortest time interval over which the motion repeats itself
Frequency (f): number of complete vibrations/sec; measure at a fixed location
Measured in Hertz (Hz)
1 Hz = 1 vibration/sec
F = 1/T

13. Example Problem p291
A sound wave has a frequency of 262 Hz. What is the time between successive wave crests?
Given: f = 262 Hz

14. Example Problem p291
A sound wave has a frequency of 262 Hz. What is the time between successive wave crests?
Given: f = 262 Hz
T=?

15. Example Problem p291
A sound wave has a frequency of 262 Hz. What is the time between successive wave crests?
Given: f = 262 Hz
T=?
F = 1/T

16. Example Problem p291
A sound wave has a frequency of 262 Hz. What is the time between successive wave crests?
Given: f = 262 Hz
T=?
f = 1/T = 1/T
T = 1/262
T = 3.82 x 10-3 s

17. Measures of a Wave
Wavelength: shortest distance between points where the wave pattern repeats itself
Represented by λ
Crests: high points of each wave
Troughs: low points of each wave
Each crest is one wavelength from the next crest; troughs are also spaced by one wavelength
V = λ / T or v = λf

18. Measures of a Wave Amplitude
Two waves with the same frequency can have different λ
Amplitude: maximum displacement from rest or equilibrium position
Example: rope shaken gently vs. violently; sound loud vs. soft; water wave giant tidal vs. ripple
To produce a wave with greater amplitude more work has to be done
Example: strong winds produce larger water waves than gentle breezes
A wave with larger amplitude transfers more energy
Double the amplitude then you increase the energy it transfers every second by a factor of 4

19. Example Problem p293
A sound wave with frequency of 262 Hz has a wavelength of 1.29 m. What is the velocity of the sound wave?

20. Example Problem p293
A sound wave with frequency of 262 Hz has a wavelength of 1.29 m. What is the velocity of the sound wave?
Given: f = 262 Hz
λ = 1.29 m

21. Example Problem p293
A sound wave with frequency of 262 Hz has a wavelength of 1.29 m. What is the velocity of the sound wave?
Given: f = 262 Hz
λ = 1.29 m
v = ?

22. Example Problem p293
A sound wave with frequency of 262 Hz has a wavelength of 1.29 m. What is the velocity of the sound wave?
Given: f = 262 Hz
λ = 1.29 m
v = ?
v = λf

23. Example Problem p293
A sound wave with frequency of 262 Hz has a wavelength of 1.29 m. What is the velocity of the sound wave?
Given: f = 262 Hz
λ = 1.29 m
v = ? v = λf
v = λf v = (1.29)(262)

24. Example Problem p293
A sound wave with frequency of 262 Hz has a wavelength of 1.29 m. What is the velocity of the sound wave?
Given: f = 262 Hz
λ = 1.29 m
v = ? v = λf
v = λf v = (1.29)(262)
v = 338 m/s