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# Waves&sound

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### Waves&sound

1. 1. Waves are all around us!Water wavesSound wavesEarthquake (seismic waves)Waves carry energy! Example: Electromagnetic waves.
2. 2. What is a wave?A wave is a disturbance that travels through space and matter, accompanied by a transfer of energy.Example: the surface of a pond is actually calm until we drop a pebble. Then the surface of the water starts to move as it is disturbed. That disturbance spreads outwards.
3. 3. Types Of WavesThere are two types of waves: 1. Transverse waves 2. Longitudinal waves
4. 4.  The direction of vibration is perpendicular to the direction of wave travel. Example: water waves, electromagnetic waves
5. 5.  The direction of vibration is parallel to the direction of wave travel. Example: sound
6. 6. VocabularyCrests / trough The high points / low points in a waveAmplitude Maximum displacement from rest positionPhase Two points that are moving in the same direction at the same speed and having the same displacement from restWavelength Shortest distance between two pointsFrequency Number of complete waves produced in 1 secondPeriod/Cycle Time taken to produce 1 complete waveWave speed Distance travelled by the wave in 1 second.
7. 7. Sound is….. A form of energy an example of longitudinal wave Produced by vibrating sources placed in a medium. (solid, liquid or gas)
8. 8.  Any medium that has particles that can vibrate will transmit sound. Solids can transmit sound best , followed by liquid then air.Application:In olden days, people would hear theground for movement.
9. 9.  Temperature?  Sound travels faster in higher temperatures Humidity?  Sound travels faster in high humidity Pressure?  Pressure has no effect on speed of sound
10. 10.  The human ear can only hear sounds of frequencies between 20 Hz and 20 kHz. Any sound with frequency higher than 20 kHz is known as ultrasound. Any sound with frequency lower than 20 Hz is known as infrasound.
11. 11.  Ultrasound is used in medical diagnosis to obtain images of internal parts of the body.  Commonly used in pre-natal examination.
12. 12.  Formation of Echoes When sound hits a hard surface, it will “bounce” off the surface. The sound that is reflected back to us is called an echo.
13. 13.  Reverberations It is the prolonged sound due to the merging of many echoes. The many echoes are produced because sound will be reflected off the different walls in a room.
14. 14.  Fishing boats use echoes to detect fish and measurement of the depth of the ocean War ships use echoes to detect mines Some animals use echoes to detect obstacles (like bats)
15. 15.  When describing a musical note as „high‟ or „low‟, we are actually talking about the pitch of the sound. Frequency affects pitch. High frequency – high pitch Lower frequency – lower pitch Shorter strings or air tunnels have higher frequency.
16. 16.  It is the volume of a sound. Loudness depends on the amplitude of the sound wave. Louder sounds have larger amplitudes and vice versa. It is measured in decibels (dB).