A student sets up a long slinky spring on a smooth floor. She sends a single pulse along the spring by moving one end sideways once. She then sends a series of continuous waves along the spring. Describe what is meant by the amplitude, wavelength, and frequency of the continuous waves, and explain how the wave speed of the continuous waves could be determined without using any electronic equipment.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
Amplitude is the maximum displacement of a point on the spring from its undisturbed position.
Wavelength is the distance between two successive identical points on the wave, e.g. crest to crest.
Frequency is the number of complete waves that pass a fixed point each second.
To find the wave speed, measure the distance a pulse travels with a ruler.
Use a stopwatch to record the time for that distance and calculate speed = distance ÷ time.
Wavelength is the distance between two successive identical points on the wave, e.g. crest to crest.
Frequency is the number of complete waves that pass a fixed point each second.
To find the wave speed, measure the distance a pulse travels with a ruler.
Use a stopwatch to record the time for that distance and calculate speed = distance ÷ time.
Examiner tips
- Use the exact definitions for amplitude, wavelength and frequency. Show the speed calculation with units. Explain the measurement set‑up clearly.
Common mistakes
- Confusing amplitude with wave height. Using the wrong distance (e.g. half a wavelength). Forgetting to divide distance by time or omitting units.
Mark scheme (5 marks)
- Amplitude is the maximum displacement of a point on the spring from its undisturbed (rest/equilibrium) position
- Wavelength is the distance from one point on a wave to the next identical/corresponding point (e.g. crest to crest or compression to compression)
- Frequency is the number of complete waves (cycles) passing a point per second / produced per second
- Measure the distance a wave (or pulse) travels using a ruler/tape measure
- Measure the time taken for the wave/pulse to travel that distance using a stopwatch, then calculate speed = distance ÷ time
Key terms in this question
amplitude · wavelength · frequency · wave speed
Related
- All Eduqas A-Level Physics revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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