AQA · A-Level · Physics
Course version: 7408 · Version from Sept 2016
Delayed acceptance of Huygens’ wave theory of light.
Full specification wording
Significance of Young’s double slits experiment (A-level only): Delayed acceptance of Huygens’ wave theory of light.
Huygens proposed that light spreads as waves, with every point on a wavefront acting as a source of secondary wavelets.
Checked against the AQA 7408 specification (opens in a new tab) on .
- Point 2 of 2
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Huygens proposed that light spreads as waves, with every point on a wavefront acting as a source of secondary wavelets. This wave theory explained reflection, refraction and diffraction, but it was not accepted quickly. Newton’s authority and his particle or corpuscular theory dominated for over a century because it explained straight-line propagation and reflection. Some wave predictions, such as diffraction, were difficult to observe with the light sources available. Young’s double slits experiment provided clear evidence for interference, which only waves can produce, and helped establish the wave theory. Acceptance was therefore delayed by scientific authority, limited evidence and the difficulty of detecting interference with early equipment.
What earns the marks
- Outline Huygens’ wave theory, including secondary wavelets spreading from a wavefront.
- State that Newton’s particle theory was favoured for a long period, partly because of Newton’s authority.
- Explain that the wave theory accounted for reflection, refraction and diffraction.
- Describe how Young’s double slits experiment produced interference fringes that supported the wave theory.
- Explain that limited observational evidence and equipment delayed acceptance of the wave theory.
- Recognise that scientific ideas can be accepted slowly when evidence is incomplete or a dominant theory exists.
Common mistakes and how to put them right
Saying that Huygens’ theory was immediately accepted.
Put it right by stating that acceptance was delayed for many decades.
Claiming that Newton supported the wave theory.
Put it right by stating that Newton favoured a particle or corpuscular theory of light.
Stating that Young invented the wave theory.
Put it right by stating that Young provided key interference evidence that supported Huygens’ earlier wave theory.
Exam tips
- Name both Huygens and Newton and contrast their theories clearly.
- Link the delay to specific factors such as authority, limited evidence and difficulty of observation.
- Use Young’s double slits experiment as the turning point that provided evidence for interference.
Try the lesson
The start of the Significance of Young’s double slits experiment (A-level only): Delayed acceptance of Huygens’ wave theory of light. lesson, made from checked teaching notes for this specification point.
Have a go first
Why was Huygens’ wave theory of light not widely accepted for many years after it was proposed?
Listen
Huygens proposed that light spreads as waves, with every point on a wavefront acting as a source of secondary wavelets. This wave theory explained reflection, refraction and diffraction, but it was not accepted quickly. Newton’s authority and his particle or corpuscular theory dominated for over a century because it explained straight-line propagation and reflection. Some wave predictions, such as diffraction, were difficult to observe with the light sources available. Young’s double slits experiment provided clear evidence for interference, which only waves can produce, and helped establish the wave theory. Acceptance was therefore delayed by scientific authority, limited evidence and the difficulty of detecting interference with early equipment. A strong answer earns marks for these points. Outline Huygens’ wave theory, including secondary wavelets spreading from a wavefront. State that Newton’s particle theory was favoured for a long period, partly because of Newton’s authority. Explain that the wave theory accounted for reflection, refraction and diffraction. Describe how Young’s double slits experiment produced interference fringes that supported the wave theory. A common slip: Saying that Huygens’ theory was immediately accepted. Instead, stating that acceptance was delayed for many decades. Exam tip: Name both Huygens and Newton and contrast their theories clearly.
Key words
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Scientific authority
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Interference as evidence for waves
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Evidence and theory
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Development of scientific ideas
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See every definition
- Scientific authority
- Newton’s authority and his particle or corpuscular theory dominated for over a century, which delayed acceptance of the wave theory.
- Interference as evidence for waves
- Young’s double slits experiment provided clear evidence for interference, which only waves can produce, and helped establish the wave theory.
- Evidence and theory
- Acceptance was delayed by scientific authority, limited evidence and the difficulty of detecting interference with early equipment.
- Development of scientific ideas
- Scientific ideas can be accepted slowly when evidence is incomplete or a dominant theory exists.
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