Electromagnetic waves form a continuous spectrum. Describe the electromagnetic spectrum, including the properties shared by all electromagnetic waves and how the waves differ from one another across the spectrum.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
All electromagnetic waves are transverse waves.
All electromagnetic waves travel at the same speed in a vacuum (3 × 10⁸ m/s).
All electromagnetic waves transfer energy from the source to an absorber.
The waves differ in frequency (and wavelength) across the spectrum.
Gamma rays have the highest frequency (and shortest wavelength) and radio waves have the lowest frequency (and longest wavelength).
All electromagnetic waves travel at the same speed in a vacuum (3 × 10⁸ m/s).
All electromagnetic waves transfer energy from the source to an absorber.
The waves differ in frequency (and wavelength) across the spectrum.
Gamma rays have the highest frequency (and shortest wavelength) and radio waves have the lowest frequency (and longest wavelength).
Examiner tips
- Use the exact wording from the mark scheme; list each point clearly.
- Show the order of the spectrum from high to low frequency.
- Remember to mention that all waves are transverse and travel at 3×10⁸ m/s.
- Include the energy transfer property.
Common mistakes
- Mixing up the order of the spectrum (e.g. putting X‑rays before gamma rays).
- Forgetting that all EM waves are transverse or that they travel at the same speed in vacuum.
- Not specifying that energy is transferred from source to absorber.
Mark scheme (5 marks)
- All electromagnetic waves are transverse waves
- All electromagnetic waves travel at the same speed in a vacuum (3 × 10⁸ m/s)
- Electromagnetic waves transfer energy from the source to an absorber
- The waves differ in frequency (and wavelength) across the spectrum
- Gamma rays have the highest frequency (and shortest wavelength) and radio waves have the lowest frequency (and longest wavelength)
Key terms in this question
electromagnetic spectrum · electromagnetic waves
Related
- All WJEC A-Level Physics (Wales) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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