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Quantum Physics

The de Broglie equation

  • 3 things to know
  • Papers 2 and 3

Overview

Recall questions on λ = h/p and on what it implies about matter.

What you need to know

Answer each one before you reveal it.

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Process

State the de Broglie equation, and how the de Broglie wavelength of a particle changes if its momentum increases.

Key term

What physical relationship does the de Broglie equation describe?

Key term

Define each symbol in the de Broglie equation λ = h/mv.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    State the de Broglie equation.

    Model answer

    λ = h/p or equivalently λ = h/mv, where λ is the de Broglie wavelength, h is the Planck constant, p is momentum, m is mass and v is velocity.

  2. 2

    What physical relationship does the de Broglie equation describe?

    Model answer

    The de Broglie equation relates the wavelength of a particle to its momentum.

  3. 3

    Define each symbol in the de Broglie equation λ = h/mv.

    Model answer

    λ is the de Broglie wavelength in metres, h is the Planck constant, m is the mass of the particle, and v is the velocity of the particle.

  4. 4

    What are the SI units of the de Broglie wavelength?

    Model answer

    Metres (m).

  5. 5

    How does the de Broglie wavelength of a particle change if its momentum increases?

    Model answer

    The de Broglie wavelength decreases as momentum increases.

  6. 6

    A particle is accelerated to a higher speed. What happens to its de Broglie wavelength?

    Model answer

    The de Broglie wavelength decreases because the particle's momentum has increased.

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