OCR · A-Level · Physics
Course version: H556 · Version from Sept 2015
Wave motion: (a) progressive waves; longitudinal and transverse waves
A progressive wave transfers energy through a medium or space without transferring matter, as the disturbance travels away from the source.
Checked against the OCR H556 specification (opens in a new tab) on .
- Point 1 of 11
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A progressive wave transfers energy through a medium or space without transferring matter, as the disturbance travels away from the source. In a transverse wave the oscillations are perpendicular to the direction of energy travel, for example a wave on a string or an electromagnetic wave. In a longitudinal wave the oscillations are parallel to the direction of travel, producing compressions and rarefactions, for example sound in air. Both types can be described by amplitude, wavelength, frequency, period and speed, with v = fλ. For a transverse wave, one wavelength is the distance between successive crests; for a longitudinal wave, it is the distance between successive compressions.
What earns the marks
- Define a progressive wave as a disturbance that transfers energy without transferring matter.
- Distinguish transverse waves, where oscillation is perpendicular to the direction of travel, from longitudinal waves, where oscillation is parallel to the direction of travel.
- Give a correct example of each type, such as a wave on a string or an electromagnetic wave for transverse, and sound in air for longitudinal.
- Identify compressions and rarefactions as features of longitudinal waves and crests and troughs as features of transverse waves.
- Relate wavelength, frequency and wave speed using v = fλ where required.
Common mistakes and how to put them right
Stating that a wave transfers matter along with energy.
Put it right: A progressive wave transfers energy, not matter, through the medium.
Confusing the oscillation direction with the direction of energy transfer.
Put it right: Transverse means oscillation perpendicular to travel, longitudinal means oscillation parallel to travel.
Describing sound as a transverse wave.
Put it right: Sound in air is longitudinal, travelling as compressions and rarefactions.
Exam tips
- Use a labelled diagram showing the oscillation direction and the direction of travel to make the transverse or longitudinal distinction clear.
- Quote a specific example for each wave type rather than a vague description.
- When using v = fλ, check that frequency is in hertz and wavelength in metres before calculating.
Try the lesson
The start of the Wave motion: (a) progressive waves; longitudinal and transverse waves lesson, made from checked teaching notes for this specification point.
Listen
A progressive wave transfers energy through a medium or space without transferring matter, as the disturbance travels away from the source. In a transverse wave the oscillations are perpendicular to the direction of energy travel, for example a wave on a string or an electromagnetic wave. In a longitudinal wave the oscillations are parallel to the direction of travel, producing compressions and rarefactions, for example sound in air. Both types can be described by amplitude, wavelength, frequency, period and speed, with v = fλ. For a transverse wave, one wavelength is the distance between successive crests; for a longitudinal wave, it is the distance between successive compressions. A strong answer earns marks for these points. Define a progressive wave as a disturbance that transfers energy without transferring matter. Distinguish transverse waves, where oscillation is perpendicular to the direction of travel, from longitudinal waves, where oscillation is parallel to the direction of travel. Give a correct example of each type, such as a wave on a string or an electromagnetic wave for transverse, and sound in air for longitudinal. Identify compressions and rarefactions as features of longitudinal waves and crests and troughs as features of transverse waves. A common slip: Stating that a wave transfers matter along with energy. Instead, a progressive wave transfers energy, not matter, through the medium. Exam tip: Use a labelled diagram showing the oscillation direction and the direction of travel to make the transverse or longitudinal distinction clear.
See it
Key words
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Progressive wave
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Transverse wave
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Longitudinal wave
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Wavelength
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See every definition
- Progressive wave
- A disturbance that transfers energy through a medium or space without transferring matter, as the disturbance travels away from the source.
- Transverse wave
- A wave in which the oscillations are perpendicular to the direction of energy travel, for example a wave on a string or an electromagnetic wave.
- Longitudinal wave
- A wave in which the oscillations are parallel to the direction of travel, producing compressions and rarefactions, for example sound in air.
- Wavelength
- For a transverse wave, the distance between successive crests; for a longitudinal wave, the distance between successive compressions.
Label the diagram
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