The de Broglie Wavelength

• What does the de Broglie equation relate to?

  Wavelength and momentum
• What happens to the angle of diffraction when electron speed increases?

  The angle of diffraction decreases
• How does wave theory relate to the de Broglie wavelength?

  Angle of diffraction decreases as wavelength decreases
• What is the relationship between momentum and de Broglie wavelength?

  Greater momentum means smaller de Broglie wavelength
• What is the de Broglie wavelength equation?

  λ = h / p
• How can the de Broglie wavelength be expressed in terms of speed?

  λ = h / mv
• How is kinetic energy related to momentum?

  E = p² / (2m)
• What is the formula for momentum in terms of kinetic energy?

  p = √(2mE)
• How does the de Broglie wavelength relate to kinetic energy?

  λ = h / (2mE)
• What are the variables in the de Broglie wavelength equation?

  • λ = de Broglie wavelength (m)
  • h = Planck’s constant (J s)
  • p = momentum (kg m s^-1)
  • E = kinetic energy (J)
  • m = mass (kg)
  • v = speed (m s^-1)
• What is the mass of a proton?

  1.67 × 10^-27 kg
• What is the mass of an electron?

  9.11 × 10^-31 kg
• How do the de Broglie wavelengths of a proton and an electron compare?

  • Ratio: λ_p / λ_e = m_e / m_p
  • λ_p is 0.0234 times smaller than λ_e
  • λ_e is about 40 times larger than λ_p
• What should you check after calculating the de Broglie wavelength?

  Perform a logic check on your answer
• What is the effect of greater mass on momentum and de Broglie wavelength?

  Greater mass leads to greater momentum and smaller wavelength