1. Waves in Action

2. WAVES

3. waves in pool link to waves in water spherelink to waves in water sphere

4. Recall…… ENERGY is the ability to push something and make it move

5. ENERGY can be transferred in two ways…

6. Transferring some matter

7. Using a WAVE

8. Types of Wave Mechanical need a medium eg Sound Water Siesmic Slinky Electromagnetic don’t need a medium eg Light Radio X ray

9. Waves travel in two different ways. Wave Types

10. Transverse waves are when the displacement is at right angles to the direction of the wave… Longitudinal waves are when the displacement is parallel to the direction of the wave…

11. wave machine

12. Wave Types go to Applet Menu > Waves

13. Water Waves

14. A A Some definitions… Amplitude (A) Wavelength ( ) Crest Trough distance from equilibrium to crest this is the distance between two corresponding points (crest to crest) Displacement (x) distance from equilibrium to to any point x

15. Period- this is the time for one wave to pass a point. It is measured in seconds (s) Frequency – this is how many waves pass a point every second. It is measured in Hertz (Hz)

16. If 20 waves pass you in one minute, what is the period of the wave? 20 waves = 60 s 1 wave =3 s T= 3s Calculate the frequency of the wave.

19. Wave Equation λ

20. Nb speed isn’t frequency…………… Stringwave The frequency of a wave is the number of waves passing in one second. (or the number of times a part of the wave wiggles in one second) The speed of a wave is the distance it travels in one second

21. SOUND Sound is produced by things vibrating. Sound travels in longitudinal waves through the air (or other medium)

22. You can hear sound in the range of approximately 20 Hz to 20,000 Hz.

23. Sound waves link to phet sound

24. We hear high frequency waves as high pitch We hear large amplitude waves as loud phet sound

25. compression rarefaction wavelength

26. Drawing a Sound Wave Sound can be analysed by an oscilloscope or a computer. It draws a graph of the wave.

27. pressure position This is a snapshot of the whole wave at one time

28. pressure time This is a movie of the pressure at one place microphone

30. Electromagnetic Waves EM waves

32. Reflection Pulses fixed end

33. Reflection of Pulses free end

34. Refraction of Pulses fast to slow

35. Refraction of Pulses slow to fast

36. Wave Reflection

38. Reflection of Waves

46. Refraction

48. DEEP SHALLOW DEEP

50. Which wave refracts most? Long wavelengths refracts most?

52. Gradual Wave Refraction

53. Interference

54. adding pulses

55. link to refraction of pulses

56. Diffraction When waves pass through a narrow gap they spread out or………Diffract. The amount of diffraction depends on the size of the gap compared with the size of the wavelength Link to Diffraction animation

59. Diffraction Link to Diffraction animation The smaller the gap, the more diffraction The bigger the wavelength, the more diffraction

62. Why can you pick up radio signals better than TV? TV waves are high frequency, short wavelength.

63. Radio waves are low frequency, long wavelength. Long wavelengths diffract more

64. Wave Interference

65. ripple tank + path diff

66. Interference of Light When light shines through a double slit interference occurs:

68. Explanation

69. in phase This produces a big wave (constructive interference) when the path difference is the waves arrive

70. when the path difference is the waves arrive out of phase This produces no wave (destructive interference)

71. We will look at interference of sound waves LINK TO phet sound Recall the definition of path difference. Recall the definition of constructive interference and destructive interference. Explain what causes the loud and quiet spots.

72. This is what you see in the ripple tank K:\PHYSICS\POWER POINT & VIDEOS\1 Light & Waves\Sound\wave-interferenceK:\PHYSICS\POWER POINT & VIDEOS\1 Light & Waves\Sound\wave-interference

73. And this is why…. http://www.schulphysik.de/suren/Applets.html

74. At an antinode, the path difference is The waves arrive in phase They add constructively and produce a big wave

75. At a node, the path difference is The waves arrive out of phase They add destructively and produce no wave

76. (extension) Young’s Equation

77. x λ θ L link to desuren wave animation d

78. link to young's expt

79. Link to factors affecting InterferenceLink to factors affecting Interference