Explain how radio waves are produced and what happens in a receiver when radio waves are absorbed.

AQA GCSE Physics (8463) — 4.6.2 Electromagnetic waves · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Radio waves are produced when an alternating current in a transmitter coil creates a changing magnetic field, which in turn induces a changing electric field – the electromagnetic wave.

When the wave reaches a receiver, the alternating electric field induces a small alternating current in the aerial.

This current has the same frequency as the transmitted radio wave and is the signal that is then amplified and demodulated to give the audio or data.

Examiner tips

  • Use the phrase ‘changing magnetic field induces a changing electric field’ to show understanding of wave generation.
  • Mention the aerial in the receiver to show the point of absorption.
  • State that the induced current is AC and at the same frequency as the wave to hit all four marks.
  • Keep the answer short and to the point – no extra explanation needed.

Common mistakes

  • Confusing the transmitter with the receiver – the wave is produced by the transmitter, not the receiver.
  • Saying the current is DC instead of AC.
  • Failing to mention that the frequency of the induced current matches the radio wave frequency.

Mark scheme (4 marks)

  1. Radio waves are produced by oscillations in electrical circuits
  2. When radio waves are absorbed (by a receiver/aerial) they create/induce a current
  3. The current produced is alternating (AC)
  4. The alternating current is at the same frequency as the radio waves

Key terms in this question

radio waves

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