12.2.1

Newton's & Huygen's Theories of Light

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Huygen's Wave Theory

Huygen believed that light traveled as a wave.

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Huygen's wave theory

  • Huygen’s agreed with other scientists that light existed as a wave.
  • He developed a general model of waves known as Huygen’s principle.
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Huygen's principle

  • Every point on a wavefront is itself a source of secondary wavelets.
  • Each wavelet will spread out as a new wave at a point source.
  • A new wavefront propagates as a tangent to the old wavefront.
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Impacts of Huygen's theory

  • Huygen’s theory explained:
    • Reflection.
    • Refraction.
    • Diffraction.
  • There was currently no evidence of diffraction, and so there was some doubt about his theory.

Newton’s Corpuscular Theory of Light

Newton's corpuscular theory was preferred to Huygens' wave theory.

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Newton's corpuscular theory

  • Newton believed that light was made of small particles called corpuscles.
  • His theory relied heavily on his widely accepted theories of motion.
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Newton's evidence

  • Newton believed his theory because light seemed to always travel in straight lines.
  • His theory explained reflection as the particle bouncing from the surface.
  • His theory explained refraction by saying that particles travel faster in a medium of higher density.
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Scientific community

  • The scientific community believed Newton’s corpuscular theory over Huygen’s wave theory.
    • Newton’s theory was more intuitive.
    • Newton had an established reputation.

Young's Double Slit Experiment

Young's double slit experiment provided evidence to support Huygen's wave theory.

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Young's double slit experiment

  • Young performed an experiment where he shone two coherent light sources through two slits.
  • An interference pattern was shown on the screen behind the slits, which suggested that the light was interfering.
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Significance of the experiment

  • Young’s experiment showed that light could behave as a wave, which gave evidence to support Huygen’s wave theory.
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Scientific community

  • Huygen’s theory was still not accepted, because of Newton’s reputation within the scientific community.
  • After a decade, Young formalised that light was a transverse wave which explains these properties, and the scientific community began to agree.

Jump to other topics

1Measurements & Errors

2Particles & Radiation

3Waves

4Mechanics & Materials

5Electricity

6Further Mechanics & Thermal Physics (A2 only)

7Fields & Their Consequences (A2 only)

8Nuclear Physics (A2 only)

9Option: Astrophysics (A2 only)

10Option: Medical Physics (A2 only)

11Option: Engineering Physics (A2 only)

12Option: Turning Points in Physics (A2 only)

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