AQA A Level Physics

Revision Notes

3.3.4 Developing Theories of EM Radiation

Developing Theories of EM Radiation

Isaac Newton (1672)

  • Newton proposed that visible light is a stream of microscopic particles called corpuscles
  • However, these corpuscles could not explain interference or diffraction effects, therefore, the view of light as a wave was adopted instead

Christiaan Huygens (1678)

  • Huygens came up with the original Wave Theory of Light to explain the phenomena of diffraction and refraction
  • This theory describes light as a series of wavefronts on which every point is a source of waves that spread out and travel at the same speed as the source wave
    • These are known as Huygens’ wavelets

Thomas Young (1801)

  • Young devised the famous double-slit experiment
  • This provided experimental proof that light is a wave that can undergo constructive and destructive interference

James Clerk Maxwell (1862)

  • Maxwell showed that electric and magnetic fields obeyed the wave equation. This means that light was simply waves made up of electric and magnetic fields travelling perpendicular to one another
  • Later, Maxwell and Hertz discovered the full electromagnetic spectrum

Albert Einstein (1905)

  • Einstein discovered that light behaves as a particle, as demonstrated by the photoelectric effect
  • He described light in terms of packets of energy called photons
  • Later the scientific community came to understand that light behaves both like a wave and a particle
    • This is known as wave-particle duality

Theories of EM radiation timeline(1), downloadable AS & A Level Physics revision notesTheories of EM radiation timeline(2), downloadable AS & A Level Physics revision notes

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Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.
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