A teacher demonstrates waves using a long slinky spring stretched along the floor. The teacher pushes and pulls one end of the spring repeatedly along its length to produce a wave. Describe the wave produced and explain how energy is transferred along the spring.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A long slinky spring is stretched along the floor. A teacher pushes and pulls one end of the spring repeatedly along its length.
Model answer (5 marks)
The wave is a longitudinal wave.
The coils of the spring vibrate parallel to the direction of the wave.
The wave consists of alternating compressions (coils pushed together) and rarefactions (coils spread apart).
Energy is transferred along the spring by the vibrating coils passing their energy to neighbouring coils; the energy travels in the same direction as the wave while the spring itself does not move along the floor.
The coils of the spring vibrate parallel to the direction of the wave.
The wave consists of alternating compressions (coils pushed together) and rarefactions (coils spread apart).
Energy is transferred along the spring by the vibrating coils passing their energy to neighbouring coils; the energy travels in the same direction as the wave while the spring itself does not move along the floor.
Examiner tips
- Use the term "longitudinal wave" first. Mention that particle motion is parallel to wave direction. Describe compressions and rarefactions. Explain energy transfer via neighbouring particles, not bulk motion.
Common mistakes
- Calling the wave transverse instead of longitudinal. Forgetting to mention that the spring does not move as a whole. Not describing both compressions and rarefactions.
Mark scheme (5 marks)
- The wave produced is a longitudinal wave
- The particles (coils) of the spring vibrate parallel to the direction of energy transfer / wave travel
- The wave consists of compressions (regions where the coils are pushed closer together)
- The wave also consists of rarefactions (regions where the coils are spread further apart)
- Energy is transferred along the spring by the vibrating particles passing on their energy to neighbouring particles / energy travels in the same direction as the wave without the spring itself moving along the floor
Related
- All WJEC A-Level Physics (Wales) revision notes →
- How to answer a "Describe and Explain" question →
- Decode the mark scheme abbreviations →
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