1. GENERAL PROPERTIES OF WAVES
INTRODUCTION TO WAVES

2. INTRODUCTION TO WAVES Throwing a pebble into a pond…
Tsunami (26 Dec 2004)

3. What is a wave? Spreading of disturbance from one place to another.
The source is a vibration or oscillation.
Energy is transferred from one point to another WITHOUT physical transfer of any material between the two points

4. Two types of waves…
Mechanical – waves that require a medium in which to travel
Electromagnetic (EM) – do not require a medium – think light!

5. Two types of Mechanical waves:
Type of Mechanical wave depends on the direction of the displacement of the wave itself.
TRANSVERSE – displacement is perpendicular to starting position
LONGITUDINAL – displacement is parallel to starting position

6. Comparing the two types:

7. THE WAVE GAME!!

8. ROPE WAVES Flash Animation of Rope Waves
What do you observe about the wave motion? How is it similar to the human wave in the wave game?

9. Transverse Waves
Transverse waves travel in a direction PERPENDICULAR to the direction of the vibrations.

10. Transverse Waves Some Examples: water waves rope waves
electromagnetic waves (example: light)

11. Test Yourself!
Rhonda sends a pulse along a rope. How does the position of a point on the rope, before the pulse comes, compare to the position after the pulse has passed?

13. The Slinky Coil
What do you notice about the direction of the vibrations and the direction of the wave?

14. LONGITUDINAL WAVES
Longitudinal waves travel in a direction PARALLEL to the direction of vibrations.
Example: Sound

15. Longitudinal Waves Rarefactions are Where the coils/particles
Spread out.
Compressions are
Where the coils/particles
Are squeezed together.

16. Compression & Rarefactions

17. Challenge
Describe how the fans in a stadium must move in order to produce a longitudinal stadium wave.

18. One more question….
A wave is transporting energy from left to right. The particles of the medium are moving back and forth in a leftward and rightward direction. What type of wave is this?
What if the particles move upward and downward?

19. THE WAVE GAME!!
Part 2

20. Crests and Troughs Crests: points of maximum displacement on a wave
Troughs: points of minimum displacement on a wave
displacement
CREST
Distance
along rope
TROUGH

21. AMPLITUDE (A) Maximum Displacement from the rest or central position.
SI unit metre (m)
displacement
crest
crest
amplitude
distance along rope
amplitude
trough

22. Wavelength (λ)
The distance between two successive points of the same phase. Example: distance between two crests. SI unit: metre (m).
displacement
crest λ
crest
amplitude
distance along rope
amplitude
trough

23. Parts on a Longitudinal Wave
Think of compressions as the crests
Think of rarefactions as the troughs

25. Frequency (f)
Number of complete waves generated per second (or number of cycles/oscillations per second)
SI unit: hertz (Hz)

26. Period (T)
Time taken to generate one complete wave (or to complete one cycle)
SI unit: second (s)

27. Relationship between T and f
As f increases, T decreases

28. Putting everything together
Try this!

29. SUMMARY

30. FOOD FOR THOUGHT
In space films, we often hear the sound of the engine of the spaceship as the zoom past each other in outer space. We even hear the spaceship firing lasers at one another. What is seriously wrong in the films?

31. FOOD FOR THOUGHT
Why don't incoming ocean waves bring more water on to the shore until the beach is completely submerged?

32. FOOD FOR THOUGHT
How will the motion of water waves change as they move from deep to shallow water? How about from shallow to deep water?
(Hint: Consider the speed of the waves)