1. Waves
S Caesar
Physics

2. Objectives In this PowerPoint the students will learn:
The properties of a wave
Behavior of Waves
Differentiate elastic & electromagnetic waves
How to calculate the period, frequency, and wave length of a wave.

3. STANDARDS –SP4
SP4
Description: SP4 Students will analyze the properties and applications of waves.
Elements: a. Explain the processes that results in the production and energy transfer of electromagnetic waves.

4. Mechanical Waves
A mechanical wave is a physical disturbance in an elastic medium.
Consider a stone dropped into a lake.
Energy is transferred from stone to floating log, but only the disturbance travels.
Actual motion of any individual water particle is small.
Energy propagation via such a disturbance is known as mechanical wave motion.

5. What are electromagnetic waves?
How electromagnetic waves are formed
How electric charges produce electromagnetic waves
Properties of electromagnetic waves

6. Electromagnetic Waves…
Do not need matter to transfer energy.
Are made by vibrating electric charges and can travel through space by transferring energy between vibrating electric and magnetic fields.

7. This page was copied from Nick Strobel's Astronomy Notes
This page was copied from Nick Strobel's Astronomy Notes. Go to his site at for the updated and corrected version.

8. Making Electromagnetic Waves
The electric and magnetic fields vibrate at right angles to the direction the wave travels so it is a transverse wave.

9. Electromagnetic Waves
These waves do not need matter to travel.
Difference between the different waves is wave length
EM spectrum illustrates the differences

10. Electromagnetic Waves
How they are formed
Kind of wave
Sometimes behave as

11. Transverse with alternating electric and magnetic fields Waves or as
Electromagnetic Waves
How they are formed
Waves made by vibrating electric and magnetic fields cthat can travel through space where there is no matter
Kind of wave
Transverse with alternating electric and magnetic fields
Sometimes behave as
Waves or as
Particles (photons)

12. WAVES
How are mechanical( elastic) waves different from electromagnetic waves ?
Differentiate them in terms of definition, their properties, examples

13. Mechanical Wave

14. Differentiate Elastic Example: Water waves Sound waves
Waves on a spring or string
Mechanical (Elastic) waves need a medium to travel
Mechanical waves transport energy and not material
Electromagnetic
Example
Microwave
X-ray, Gamma ray
Light waves, UV rays
Do not need a medium to travel
It travels with very high speed
Can be described by their wavelength, energy, and frequency

15. Cont’d Requires initial energy input be created
Mechanical waves cause displacement of the matter through which the wave is traveling
Mechanical waves vibrations can put air molecules in motion
Very low energy and frequency
Big wavelength
Remember that energy gets transferred and not materials
Electromagnetic waves cause no displacement of matter and can transfer energy in the absence of matter
Do not need to take place in any media vibrations
Very high energy and high frequency
Electromagnetic vibrations do not put our molecules in motion

16. Types of Waves Mechanical Waves Electromagnetic Waves
A wave is a method of transferring energy from one place to another without transferring matter.
Mechanical waves are those that require a medium for their transfer and include
water waves, sound waves and waves in stretched strings.
Electromagnetic waves consist of varying electric and magnetic fields.
The two fields are perpendicular to each other and to the direction of travel of the wave.
Each vibrates with high frequency -

17. Objectives In this PowerPoint the students will learn:
Demonstrate your understanding of transverse and longitudinal waves.
Define, relate and apply the concepts of frequency, wavelength, and wave speed.
Solve problems related to them.

18. A Transverse Wave
In a transverse wave, the vibration of the individual particles of the medium is perpendicular to the direction of wave propagation.
Motion of particles
Motion of wave

19. Longitudinal Waves
In a longitudinal wave, the vibration of the individual particles is parallel to the direction of wave propagation. v
Motion of wave
Motion of particles

20. Production of a Longitudinal Wave
An oscillating pendulum produces condensations and rarefactions that travel down the spring.
The wave length l is the distance between adjacent condensations or rarefactions.

21. Sound Sound is produced when an object vibrates.
When an object vibrates it exerts a force on the surrounding
Sound is a mechanical wave (requires a medium to travel and they are compression wave (molecules colliding).
The medium sound travels through are of Air.
Loudness of a sound is recorded in decibels
As a sound gets louder, the amplitude of the wave increases

22. Water Waves
An ocean wave is a combi-nation of transverse and longitudinal.
The individual particles move in ellipses as the wave disturbance moves toward the shore.

23. What is a wave? A wave is a disturbance which moves through a medium.
Water waves and sound waves are examples of mechanical waves.
Light waves are not considered mechanical waves. They are electromagnetic in nature.

24. What is an amplitude?
Amplitude: the height of the wave, measured in meters.

25. What are frequency waves?
Frequency: the number of complete waves that pass a point in one second, measured in inverse seconds, or Hertz (Hz).

26. What are transverse waves?
Speed: the horizontal speed of a point on a wave as it propagates, measured in meters / second.
Speed of wave, v = frequency

27. Terminology Amplitude: Height of Wave (m)
Wave Length: distance from one wave top, or crest, to the immediate next. (m)
Phase Shift: how far to the left or right the wave slides. (m)
Frequency: refers to how many waves are made per time interval. This is usually described as how many waves are made per second, or as cycles per second. (hz)
Crest: top most part of the wave
Trough: bottom most part of the wave
Period: the time needed to repeat one complete cycle of motion.

28. Frequency and Wavelength
Transverse Waves (cont.)
Frequency and Wavelength
As frequency increases wavelength decreases
As frequency decreases wavelength increases

29. What is wavelength?
Wavelength: the distance between adjacent crests, measured in meters.

30. Velocity and Wave Frequency.
The period T is the time to move a distance of one wavelength. Therefore, the wave speed is:
The frequency f is in s-1 or hertz (Hz).
The velocity of any wave is the product of the frequency and the wavelength:

31. Problem #1
What is the speed of a periodic wave disturbance that has a frequency of 3.5 Hz and a wavelength of 0.7 m?
Given f= 3.5 Hz &
V= f x V=

32. Problem #1
What is the speed of a periodic wave disturbance that has a frequency of 3.5 Hz and a wavelength of 0.7 m?
V= f x
V= 3.5 x 0.7= 2.45 m/s

33. Example 2: An electromagnetic vibrator sends waves down a string
Example 2: An electromagnetic vibrator sends waves down a string. The vibrator makes 600 complete cycles in 5 s. For one complete vibration, the wave moves a distance of 20 cm. What are the frequency, wavelength, and velocity of the wave?
f = 120 Hz
v = fl
The distance moved during a time of one cycle is the wavelength; therefore:
v = (120 Hz)(0.02 m)
l = m
v = 2.40 m/s

34. Problem #2
An ocean wave has a length of 12.0 m. A wave passes a fixed location every 3.0 s. What is the speed of the wave?
Given d= 12.0 m
t= 3.0 s
v= d / t
v= (12/3)= 4.0 m/s

35. Problem #2
An ocean wave has a length of m. A wave passes a fixed location every 9.0 s. What is the speed of the wave?
v= d / t V=