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…
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
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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.
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 .
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
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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
