Starter quiz
- How does a loud speaker move to make a sound wave that moves forwards?
- up and down
- side to side
- forwards and backwards ✓
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- How do air particles move as a sound wave moves forwards through the air?
- side to side
- forwards and backwards ✓
- forwards with the wave
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- A sound wave is an example of a ______ wave.
- 'longitudinal' ✓
- What is the wave medium of a longitudinal wave travelling along a spring stretched across a table?
- the air
- the spring ✓
- the table
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- What is the maximum displacement of a particle in a wave called?
- wavelength
- period
- frequency
- amplitude ✓
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- What is the name given to the number of complete wave cycles passing a point each second?
- period
- frequency ✓
- displacement
- amplitude
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Exit quiz
- How do particles in a soundwave move?
- they oscillate backwards and forwards and do not move along the wave ✓
- they oscillate backwards and forwards as they move along the wave
- they move along the wave without oscillating
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How far do the particles in a soundwave vibrate?- they vibrate between one end of the wave and the other
- they vibrate between one compression and the next
- they vibrate less than the distance between one compression and the next ✓
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- What is the amplitude of a longitudinal wave?
- the distance between two compressions
- the maximum displacement of the wave ✓
- the distance between a compression and a rarefaction
- the wavelength of the wave
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What is the distance between two wave crests on a displacement-distance graph equal to?- the amplitude
- the frequency
- the period
- the wavelength ✓
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- What does a positive displacement in a longitudinal wave indicate about that part of the wave?
- it is behind its rest position
- it is in front of its rest position ✓
- it is at its rest position
- it is above its rest position
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- What does a negative displacement in a longitudinal wave indicate about that part of the wave?
- it is behind its rest position ✓
- it is in front of its rest position
- it is above its rest position
- it is below its rest position
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Worksheet
Presentation
Video
Lesson Details
Key learning points
- In a longitudinal wave, the oscillations / vibrations are in the same direction in which the wave travels.
- Displacement is the distance one part of a wave is moved away from its rest position.
- In a longitudinal wave, forwards displacement is positive and backwards displacement is negative.
- Wavelength of a longitudinal wave is the distance between one compression (or rarefaction) and the next.
Common misconception
Particles in a longitudinal wave move forward and backward between one compression and the next.
Demonstrate the movement of a candle flame in front of a loudspeaker set to a very low frequency with a wavelength of about 30 m (at 10 Hz).
Keywords
Longitudinal wave - each part of a longitudinal wave oscillates forward and backward in the same direction in which the wave moves.
Compression - part of a longitudinal wave in which parts of the wave are squashed closer together is called a compression.
Rarefaction - part of a longitudinal wave in which parts of the wave are spaced further apart is called a rarefaction.
Wavelength - the wavelength of a longitudinal wave is the distance along the wave between one compression and the next.
Amplitude - the amplitude of a longitudinal wave is the maximum distance each part of the wave moves forward or backward.