EM Waves & Atoms (OCR GCSE Physics A, Combined (Gateway Science Suite)): Revision Notes

6.2.6 EM Waves & Atoms

Atoms and EM Radiation

Electron Orbit Changes

• When electrons change orbit (move closer or further from the nucleus):
  • Absorption:
  • When electrons move to a higher orbit (further from the nucleus).
  • The atom has absorbed EM radiation.
  • Emission:
  • When the electron falls to a lower orbit (closer to the nucleus).
  • The atom has emitted EM radiation.
• If an electron gains enough energy, it can leave the atom to form an ion.
• Gamma rays originate from changes in the nucleus of an atom.

Hazards

• UV light, X-rays, and gamma rays can have hazardous effects on human body tissue.
• The effects depend on the type of radiation and the size of the dose.
• Radiation Dose:
  • How much exposure leads to harm for a person?
  • UV:
  • Skin ages prematurely, increasing the risk of skin cancer.
  • Sun cream prevents over-exposure in summer.
  • X-ray and Gamma:
  • Ionisation radiation can cause the mutation of genes, causing cancer.
  • Minimal exposure should be ensured.

Uses of EM Waves

• Radio:
  • TV and radio.
  • The long wavelength can travel far without losing quality.
• Microwave:
  • Satellite communication, cooking food.
  • Can penetrate the atmosphere to reach satellites.
• Infrared (IR):
  • Cooking food, infrared cameras.
  • Transfers thermal energy.
• Visible Light:
  • Fibre optics.
  • Best reflexion/scattering in glass (others have too short/long wavelengths).
• Ultraviolet (UV):
  • Sun tanning, energy-efficient lamps.
  • Radiates the least heat but more energy.
• X-ray:
  • Medical imaging and treatment (and gamma).
  • Very high in energy and can penetrate material easily.