1. Waves in Action

2. WAVES

10. Waves travel in two different ways.

11. 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…

12. wave machine

14. Water Waves

15. Some definitions… Amplitude (A) Wavelength (  ) 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 A A Crest Trough

17. 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.

20. Wave Equation λ

23. How does ultrasound work? Ultrasonic waves are partly reflected at the boundary as they pass from one medium to another. The time taken for these reflections can be used to measure the depth of the reflecting surface. This information is used to build up a picture of the object. Ultrasound is the region of sound above 20,000Hz – it can’t be heard by humans. It can be used in pre-natal scanning:

24. Other uses of ultrasound 1) Echo sounding The ultrasound is reflected from the sea floor. 2) Breaking down kidney stones Ultrasonic waves break kidney stones into much smaller pieces 3) Cleaning (including teeth) Ultrasound causes dirt to vibrate off without damaging the object

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

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

28. compression rarefaction wavelength

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

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

33. DataStudio (2)

34. High frequency Low frequency

38. Reflection Pulses fixed end

39. Reflection of Pulses free end

40. Refraction of Pulses fast to slow

41. Refraction of Pulses slow to fast

42. Wave Reflection

43. Reflection of Waves

51. Refraction

53. DEEP SHALLOW SHALLOW DEEP

55. Gradual Wave Refraction

56. Interference

59. 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 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

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

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

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

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