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Year 11 - Science

Ionising electromagnetic radiation

Electromagnetic waves

Unit Summary

This unit explores reflection, refraction, and lenses using ray diagrams. It covers the electromagnetic spectrum, light as a wave, absorption, transmission, and practical uses. Emphasis is on risks, temperature balance, data presentation, and unit conversions.

Lesson Summary

You will learn to explain the properties, uses and dangers of ionising electromagnetic radiation.

Key Notes

  • All EM waves can transfer energy, from a source to an absorber.
  • Only UV, X-ray and gamma frequencies of EM wave cause ionisation. The higher the frequency, the more ionising.
  • Ionising radiation can damage cells, cause genes to mutate and increase the risk of cancer.
  • UV is used in lighting and to disinfect water. It causes tanning/sunburn. It increases the risk of skin cancer.
  • X- and gamma rays are used in medical imaging. Gamma rays are used to kill cancer cells and to sterilise food/equipment.

Vocabulary To Learn

  • energy transfer: Electromagnetic waves transfer energy because stores of energy decrease when they are emitted and increase when they are absorbed.
  • ionisation: Ionisation is the process of an atom losing or gaining electrons so become charged/becoming an ion.
  • ultraviolet: Ultraviolet means EM radiation with frequencies greater than visible light but lower than X–rays.
  • X-rays: X-rays are EM radiation with frequencies greater than ultraviolet but lower than gamma rays.
  • gamma rays: Gamma rays are the highest frequency electromagnetic waves.

Common Mistakes To Avoid

  • Gamma rays are always higher energy (or power), or more dangerous, than other frequencies of EM radiation.

3 Quick Questions (With Answers)

1. Explain the scientific idea in this lesson using two key points.

All EM waves can transfer energy, from a source to an absorber. Only UV, X-ray and gamma frequencies of EM wave cause ionisation. The higher the frequency, the more ionising.

2. Define this scientific word and use it in context. 'energy transfer'

Electromagnetic waves transfer energy because stores of energy decrease when they are emitted and increase when they are absorbed. Include the word in a full scientific explanation, not as a single label.

3. Correct this common scientific misunderstanding.

Mistake: Gamma rays are always higher energy (or power), or more dangerous, than other frequencies of EM radiation. Correction: EM waves transfer their energy in 'chunks' or 'packets'. The energy transferred by one 'packet' of radiation (and so its ionising ability) does depend on frequency. But the power of a beam of radiation depends on the intensity of the radiation too.

More Lessons In This Unit

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