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PHYSICS – Sound

PHYSICS – Sound. LEARNING OBJECTIVES. What is a wave?. A wave is an oscillation that moves through space, transferring energy from one place to another. Which of these is not an example of a wave?.

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PHYSICS – Sound

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  1. PHYSICS – Sound

  2. LEARNING OBJECTIVES

  3. What is a wave? A wave is an oscillation that moves through space, transferring energy from one place to another. Which of these is not an example of a wave? All true waves move or propagate through space, therefore the ripples on a sand dune are not waves.

  4. Representing waves There are two main ways of representing a wave on a graph. • graphing an oscillation in time: amplitude y t period This graph represents how y changes with time. It could be an oscillation of voltage, displacement, pressure, or any other suitable variable, depending on the context.

  5. Sound What is sound?

  6. Sound What is sound? Sound is a series of waves (sound waves) caused by vibrations.

  7. Sound What is sound? When a drum is struck, the skin vibrates backwards and forwards very quickly, sending sound waves through the air to your ears. Sound is a series of waves (sound waves) caused by vibrations.

  8. Sound What is sound? When a drum is struck, the skin vibrates backwards and forwards very quickly, sending sound waves through the air to your ears. Sound is a series of waves (sound waves) caused by vibrations. Sound waves travel as a series of compressions and rarefactions through the air. They are longitudinal waves.

  9. Waves transfer energy without transferring matter. Frequency= waves/time

  10. Pressure Higher frequency sounds (higher pitch) mean that the speaker vibrates backwards and forwards more often

  11. Longitudinal Waves Eg. Sound http://www.physicsclassroom.com/class/sound/Lesson-1/Sound-as-a-Longitudinal-Wave

  12. Longitudinal Waves Eg. Sound http://www.physicsclassroom.com/class/sound/Lesson-1/Sound-as-a-Longitudinal-Wave Compression Rarefaction

  13. Longitudinal Waves Eg. Sound http://www.physicsclassroom.com/class/sound/Lesson-1/Sound-as-a-Longitudinal-Wave Compression Rarefaction In longitudinal waves the oscillations (vibrations) are backwards and forwards. The different sections are known as compressions and rarefactions.

  14. Longitudinal Waves Eg. Sound http://www.physicsclassroom.com/class/sound/Lesson-1/Sound-as-a-Longitudinal-Wave Compression Rarefaction In longitudinal waves the oscillations (vibrations) are backwards and forwards. The different sections are known as compressions and rarefactions. The oscillations in longitudinal waves are in the direction of travel. Sound waves are longitudinal waves.

  15. Polarization Electromagnetic waves (such as light) ‘oscillate’ in three dimensions, shown by the green and the blue waves below: unpolarized wave polarized wave polarizing filter When these waves pass through a polarizing filter, only one plane is able to get through (the blue one in this case). The other parts of the wave are blocked. This is polarization. If another slit at 90 degrees is placed in the waves path, then none of the wave can get through.

  16. Sound Waves

  17. Sound Waves Sound Wave – Key Fact Sound waves are longitudinal waves.

  18. Sound Waves Sound Wave – Key Fact Sound waves need a medium (material) to travel through – they cannot travel through a vacuum (empty space)

  19. Sound Waves Sound Wave – Key Fact Sound waves can travel through solids, liquids and gases.

  20. Speed of Sound Sound travels at 330 metres per second (330m/s), or 760 mph.

  21. Speed of Sound Lightning travels much faster than the sound of thunder. Sound travels at 330 metres per second (330m/s), or 760 mph. A 3 second gap between the flash of lightning and the sound of thunder means that the storm is about a kilometre away.

  22. Speed of Sound Lightning travels much faster than the sound of thunder. Sound travels at 330 metres per second (330m/s), or 760 mph. A 3 second gap between the flash of lightning and the sound of thunder means that the storm is about a kilometre away.

  23. Speed of Sound Lightning travels much faster than the sound of thunder. Sound travels at 330 metres per second (330m/s), or 760 mph. A 3 second gap between the flash of lightning and the sound of thunder means that the storm is about a kilometre away.

  24. Speed of Sound Lightning travels much faster than the sound of thunder. Sound travels at 330 metres per second (330m/s), or 760 mph. A 3 second gap between the flash of lightning and the sound of thunder means that the storm is about a kilometre away.

  25. Speed of Sound Lightning travels much faster than the sound of thunder. Sound travels at 330 metres per second (330m/s), or 760 mph. A 3 second gap between the flash of lightning and the sound of thunder means that the storm is about a kilometre away. Air (dry) at 0oC = 330m/s, water at 0oC = 1400m/s, concrete = 5000m/s

  26. How could we calculate the speed of sound in air?

  27. How could we calculate the speed of sound in air? SPEED = DISTANCE TIME

  28. How could we calculate the speed of sound in air? SPEED = DISTANCE TIME 75 metres

  29. How could we calculate the speed of sound in air? SPEED = DISTANCE TIME 75 metres 75 metres

  30. How could we calculate the speed of sound in air? SPEED = DISTANCE TIME 75 metres 75 metres Time

  31. How could we calculate the speed of sound in air? SPEED = DISTANCE TIME Speed = 150 333 m/s 0.45 75 metres 75 metres Time

  32. You need a quiet open space at least 100m long to perform this investigation. 100m START STOP 1. When you see the cymbals crash, press START. 2. When you hear the cymbals crash, press STOP.

  33. Stand at least 100m from a large, flat wall with a stop watch. Measuring speed with echos START 150m STOP 1. Use a starting pistol (or clapper board) to make a sound. 2. Measure the time taken between firing the pistol and hearing the echo. How far does the sound travel?

  34. Are particles needed for sound to travel?

  35. Are particles needed for sound to travel?

  36. Are particles needed for sound to travel?

  37. Are particles needed for sound to travel? As the vacuum pump is switched on, air is drawn out of the bell jar. The bell begins to get quieter.

  38. Are particles needed for sound to travel? As the vacuum pump is switched on, air is drawn out of the bell jar. The bell begins to get quieter. Eventually, all of the air particles will have been drawn out of the bell jar. We can see the bell ringing, but we can’t hear it

  39. Are particles needed for sound to travel? Conclusions: Sound needs particles to travel. Sound cannot travel through a vacuum. Sound cannot travel through space, because there are no particles.

  40. Will sound travel faster through a solid, liquid or gas?

  41. Will sound travel faster through a solid, liquid or gas?

  42. Will sound travel faster through a solid, liquid or gas? Sound travels faster through a solid because the particles are more densely packed together.

  43. Will sound travel faster through a solid, liquid or gas? Concrete = 5000m/s, Water at 0oC = 1400m/s, Air (dry) at 0oC = 330m/s Sound travels faster through a solid because the particles are more densely packed together.

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