1. Making Waves

2. Objectives
To investigate the basic nature of waves and their properties.
Wave Properties: Speed, Wavelength, Frequency, and Period.
Wave Phenomena: Reflection, Interference, and Transmission.
Epic wave video

3. Ocean Waves A wave is a traveling disturbance.
A wave carries energy from place to place without any transfer of matter.

4. Some waves such as mechanical waves (eg sound waves) require a medium in which to travel.
Electromagnetic waves (eg. Light) are able to travel through a vacuum ie they do not require a medium.

5. A pulse is a single wave of short duration.
Most waves repeat the same motion in a regular pattern – they are periodic.

6. Types of waves

7. Transverse waves
A transverse wave is one in which the disturbance is perpendicular to the direction of travel (propagation) of the wave.
Examples: Light wave, waves on a guitar string.

8. Longitudinal Waves
Longitudinal wave is one in which the disturbance is parallel to the line of travel (propagation) of the wave.
Example: Sound wave in air is a longitudinal wave.

9. State 2 differences between sound and light waves

10. 1. Sound is longitudinal, light is transverse
2. Sound requires a medium

11. Seismic Waves Wave Type Motion of particles Velocity
Other characteristics
Longitudinal (P)
Same as direction of propagation
Faster ~6Km/s
Travel through liquids
Transverse (S)
Perpendicular to direction of propagation
Slower ~3Km/s
Do not travel through liquids

12. What is a periodic wave?
Periodic waves are waves that repeat.

14. Amplitude, Wavelength, and Period
The amplitude, A is the maximum disturbance.
The wavelength, λ  is the horizontal length of one cycle of the wave .eg. The distance between two crests.
The period, T is the time required for one complete up/down cycle of the wave.
The Wave velocity, v is the velocity of the wave shape.

15. Frequency
The frequency, f is the number of waves passing any point each second.
The frequency is measured in hertz (Hz)
Link

16. Wave Speed

17. Example
Sound travels at 330 m/s in air. What will be the wavelength of a note with frequency 110 Hz?

18. Waves on a Rope

19. Pulses reflecting and transmitting
Link

20. Superposition
Link
When 2 waves meet they can interfere with one another.
2 peaks or troughs coinciding form a wave twice as large – constructive interference.
A peak and trough coinciding can “cancel” each other – destructive interference.
Another link

21. Standing waves
If two waves of the same amplitude, frequency and speed are produced from the ends of a hollow pipe or string then a standing wave forms.

22. Nodes and antinodes
Where two wave peaks meet, a maximum displacement – antinode – forms.
Peak and trough “cancel out” to form node.

23. Diffraction
Link
As a wave passes an object diffraction occurs – the wave bends.
Longer the wavelength the greater the diffraction.(Sound more than light)
A gap between two obstacles the same size as the wavelength gives maximum effect.

24. Interference

26. Periodic Wave

27. Harmonic Wave

28. The Speed of Wave on a String

29. Guitar
The strings on a steel-string guitar have different weights, µ = m/L.

30. Q13

31. Principle of Superposition
When two or more waves are present simultaneously at the same place, the resultant disturbance is the sum of the disturbances from the individual waves.

32. Constructive Interference of Sound Waves

33. Destructive Interference

34. Standing Waves

35. Nodes and Antinodes

36. What determines the frequency of a wave on a guitar string?

37. Making music with soft-drink bottles

38. Longitudinal Standing Waves
Musical instruments in the wind family depend on longitudinal standing waves in producing sound. Since wind instruments (trumpet, flute, clarinet, pipe organ, etc.) are modified tubes or columns of air, it is useful to examine the standing waves that can be set up in such tubes.

39. Standing-Wave Patterns

40. Doppler Effect

41. Doppler Effect