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Waves and the particle nature of light
Quick questions on Wave-particle duality: de Broglie wavelength and electron diffraction - Edexcel A-Level Physics
5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the de Broglie wavelength?Show answer
Because is tiny, everyday objects have an immeasurably small wavelength and never show wave behaviour. Only very low-mass, fast particles such as electrons have wavelengths comparable to atomic spacings, which is why their wave nature is observable. For an electron accelerated through a potential difference , the kinetic energy gives the speed and hence the wavelength.
What is complementary models of light?Show answer
The wave model of light explains refraction, diffraction, interference and polarisation; the photon model explains the photoelectric effect, line spectra and the energy of individual quanta. Neither model alone is complete; they are complementary, each correct within its domain. The same is true for matter: an electron is described by a wave for diffraction but as a localised particle when it strikes a detector.
What is q1?Show answer
State the de Broglie relationship. [1 mark]
What is q2?Show answer
A proton (mass kg) moves at m per second. Find its de Broglie wavelength. Take J s.
What is q3?Show answer
Explain why everyday objects do not show wave behaviour. [2 marks]
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