2. Objectives
At the end of this section, the student will be able to:
Distinguish local particle vibrations from overall wave motion.
Differentiate between pulse waves and periodic waves.
Differentiate between mechanical and electromagnetic waves
Interpret waveforms of transverse and longitudinal waves.
Relate energy and amplitude.
Distinguish between period and frequency.
Apply the relationship among wave speed, frequency, and
wavelength to solve problems.
4. Wave Motion
A wave is the motion of a disturbance.
A medium is a physical environment through which a disturbance
can travel. For example, water is the medium for ripple waves in a
pond.
A wave transports energy and not matter.
Objective: Distinguish local particle vibrations from overall wave motion.
10. Mechanical and electromagnetic waves
Click on the picture below to watch the video
Objective: Differentiate between mechanical and electromagnetic waves
12. Objective: Differentiate between mechanical and electromagnetic waves
Mechanical and electromagnetic waves
A mechanical wave requires a medium to propagate
An electromagnetic wave doesnt require a
medium to propagate, it can propagate in vacuum
Example: Sound waves
Example: Light waves
14. Transverse waves
A transverse wave is a wave whose particles vibrate
perpendicularly to the direction of the wave motion.
The crest is the highest point above the equilibrium position,
and the trough is the lowest point below the equilibrium
position.
The wavelength (l) is the distance between two adjacent
similar points of a wave.
Objective: interpret waveforms of transverse and longitudinal waves.
16. Longitudinal Waves.
Click on the wave below to watch the video
Objective: interpret waveforms of transverse and longitudinal waves.
17. A longitudinal wave is a wave whose particles vibrate
parallel to the direction the wave is traveling.
Longitudinal Waves.
Objective: interpret waveforms of transverse and longitudinal waves.
18. Waves and Energy Transfer
Waves transfer energy by the vibration of matter.
The greater the amplitude, the more energy a wave carries.
The amplitude of a wave gradually diminishes over time as its
energy is dissipated.
Objective: Relate energy and amplitude.
19. Self Check
Multiple Choice
Base your answers on the graph.
1. Which letter on the graph represents wavelength?
F. A H. C
G. B J. D
20. Self Check
Multiple Choice
Base your answers on the graph.
1. Which letter on the graph represents wavelength?
F. A H. C
G. B J. D
21. Self Check
Multiple Choice
Base your answers on the graph.
2. Which letter on the graph is used for a trough?
A. A C. C
B. B D. D
22. Self Check
Multiple Choice
Base your answers on the graph.
2. Which letter on the graph is used for a trough?
A. A C. C
B. B D. D
23. Self Check
Multiple Choice
Base your answers on the graph.
3. What kind of wave does this graph represent?
A. transverse wave C. electromagnetic wave
B. longitudinal wave D. pulse wave
24. Self Check
Multiple Choice
Base your answers on the graph.
3. What kind of wave does this graph represent?
A. transverse wave C. electromagnetic wave
B. longitudinal wave D. pulse wave
27. Period and Frequency of a SHM
Objective: Distinguish between period and frequency.
Click on the image
28. Period and Frequency of a SHM
The frequency
It is the number of cycles (oscillations) performed in a unit of time.
Its SI unit is the Hertz (Hz)
Its symbol is f.
= / , where n is the number of cycles and t is the time.
The period
It is the time taken to perform one oscillation.
Its SI unit is the second (s)
Its symbol is T.
Objective: Distinguish between period and frequency.
29. Period and Frequency of a Periodic Wave
A periodic wave is often created by a SHM.
All the points in the medium will have the same SHM as the source.
The created wave has the same period and frequency as the SHM.
A wave frequency is the number of waves that pass a fixed point per
unit of time.
A wave period is the time taken to complete 1 cycle. In one period
the wave travels 1 wavelength l.
Objective: Distinguish between period and frequency.
30. Period and Frequency of a Periodic Wave
Objective: Distinguish between period and frequency.
Click on the image
31. Speed of propagation of a wave
The speed of a mechanical wave is constant for any given medium.
The speed of a wave is given by the following equation:
v = f .
wave speed = frequency wavelength
This equation applies to both mechanical and electromagnetic waves.
33. Self Check
Multiple Choice
1. Two successive crests of a transverse wave are 1.20 m
apart. Eight waves pass a given point in 16.0 s. What is
the wave speed?
F. 0.667 m/s
G. 0.800 m/s
H. 1.80 m/s
J. 9.60 m/s
34. Self Check
Multiple Choice
1. Two successive crests of a transverse wave 1.20 m
apart. Eight waves pass a given point in 16.0 s. What is
the wave speed?
F. 0.667 m/s
G. 0.600 m/s
H. 1.80 m/s
J. 9.60 m/s
了 = 1.20 m
f = n/t = 8/16.0 = 0.500Hz
V = 了 . f = 1.20 x 0.500 = 0.600 m/s
35. Self Check
Short Response
2. Green light has a wavelength of 5.20 107
m and a
speed in air of 3.00 108
m/s. Calculate the
frequency and the period of the light.
f = v/了 = 3.00 108
/ 5.20 107
= 5.77 x1014
Hz
T = 1/f = 1.73 x 10-15
s
36. Self Check
Short Response
3. What kind of waves does not need a medium through
which to travel?
Answer: electromagnetic waves