Using ideas based upon the quantum theory and Einstein’s theory of relativity, de Broglie suggested that the momentum (p) of a particle and its associated wavelength (λ) are related by the equation:
Since momentum p = mv, the de Broglie wavelength can be related to the speed of a moving particle (v) by the equation:
Since kinetic energy E = ½ mv2
Momentum and kinetic energy can be related by:
Combining this with the de Broglie equation gives a form which relates the de Broglie wavelength of a particle to its kinetic energy:
Where:
λ = the de Broglie wavelength (m)
h = Planck’s constant (J s)
p = momentum of the particle (kg m s-1)
E = kinetic energy of the particle (J)
m = mass of the particle (kg)
v = speed of the particle (m s-1)
Worked Example
A proton and an electron are each accelerated from rest through the same potential difference.