A radio station broadcasts signals using electromagnetic waves. Explain what is meant by the terms wavelength, frequency, and period for these waves, and state the relationship between wave speed, frequency, and wavelength.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Radio waves are a type of electromagnetic wave. All electromagnetic waves travel at the same speed in a vacuum.
Model answer (5 marks)
Wavelength is the distance between two successive identical points on a wave, for example crest to crest or trough to trough.
Frequency is the number of complete waves (oscillations or cycles) that pass a fixed point each second.
Period is the time taken for one complete wave to pass a fixed point.
The period is equal to 1 divided by the frequency (T=1/f), or conversely the frequency is 1 divided by the period.
The speed of a wave is the product of its frequency and its wavelength: v= f\,\lambda.
Frequency is the number of complete waves (oscillations or cycles) that pass a fixed point each second.
Period is the time taken for one complete wave to pass a fixed point.
The period is equal to 1 divided by the frequency (T=1/f), or conversely the frequency is 1 divided by the period.
The speed of a wave is the product of its frequency and its wavelength: v= f\,\lambda.
Examiner tips
- Use the exact definitions of wavelength, frequency and period. Show the relationship v=f\,\lambda and T=1/f. Keep the answer concise and to the point.
Common mistakes
- Confusing wavelength with wavelength of a different wave. Using the wrong formula for period (e.g. T=f instead of T=1/f). Omitting the relationship between speed, frequency and wavelength.
Mark scheme (5 marks)
- Wavelength is the distance from one point on a wave to the next identical point (e.g. crest to crest or trough to trough)
- Frequency is the number of complete waves (oscillations/cycles) passing a point per second
- Period is the time taken for one complete wave (oscillation/cycle) to pass a point
- Period is equal to 1 divided by frequency (or frequency is 1 divided by period)
- Wave speed equals frequency multiplied by wavelength
Key terms in this question
wavelength · frequency · period · wave speed
Related
- All WJEC A-Level Physics (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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