Sound and Ultrasound

franfrog10
Mind Map by franfrog10, updated more than 1 year ago
franfrog10
Created by franfrog10 about 6 years ago
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Cambridge IGCSE Physics (2.Waves) Mind Map on Sound and Ultrasound, created by franfrog10 on 03/31/2014.
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Sound and Ultrasound
1 Sound waves are LONGITUDINAL
1.1 they are caused by mechanical vibrations in a substance
1.2 vibrations are PARALLEL to the direction of travel
2 Human ears can hear frequencies from 20Hz to 20,000Hz
2.1 the ability to hear higher frequencies declines with age
3 Sound waves can be reflected to produce ECHOES

Annotations:

  • When calculating the distance of a reflecting surface from a person, remember that an echo goes there and back (divide by two) E.G. Sound travels at 340m/s. A person hears an echo 0.4 seconds after shouting - how far away is the reflecting surface? (340 x 0.4) = 136 136/2 = 68m
3.1 only hard, flat surfaces can reflect sound
3.1.1 e.g. flat walls & floors
3.2 Soft objects/surfaces absorb sound
3.2.1 e.g. carpets, curtains & furniture
4 Sound waves can also be DIFFRACTED
4.1 the WAVELENGTH should be of the same order as the size of the obstacle or gap that diffracts the waves
5 FREQUENCY
5.1 determines the PITCH of a sound
5.1.1 the higher the frequency the higher the pitch
5.2 = the number of vibrations each second
5.3 measured in Hertz (Hz)
6 AMPLITUDE
6.1 determines the LOUDNESS (VOLUME) of a sound
6.1.1 the greater the amplitude, the more energy the wave carries and the louder the sound
6.2 the 'height' of the wave
7 OSCILLOSCOPE
7.1 a device used to display the shape of an electrical wave
7.2 a short wavelength on the screen corresponds to a high frequency
8 ULTRASOUND
8.1 waves with frequencies higher than 20,000Hz (20MHz)
8.2 non-ionising (safer than X-rays)
8.3 used for pre-natal scanning or to break down kidney stones so that they could be removed
8.4 Ultrasound scanners use a transducer to produce and detect ultrasound waves

Annotations:

  • Again, the echoes are going there AND back, so the calculations will probably be halved again
8.4.1 pulses of ultrasound are directed into the body
8.4.1.1 they partially reflect from the tissue boundaries
8.4.1.1.1 the reflected pulses are detected by the transducer
9 s = v x t
9.1 distance (between interfaces in various media) = wave speed x time taken
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