If a photons have
momenta… do particles
have wavelengths?
Yes!
de Broglie wavelength:
h
h
  or p 
p

electrons can only exist in orbitals where the circumference
was is equal to whole number multiples of wavelengths of the
electrons.
http://www.walter-fendt.de/ph11e/bohrh.htm
Only small, high speed particles will show noticeable wave
characteristics (diffraction, interference)
 the wavelengths of elementary particles are the size
of nuclei or smaller
This particle-wave duality
of matter makes it
impossible to develop a
set of equations that tells
us both exactly where an
electron is and what its
momentum might be.
Davisson and Germer reflected a
beam of electrons off a crystal and
obtained a series of maxima and
minima patterns (just like a beam
of light would give a series of light
and dark bands when it passed
through a diffraction grating)
Interference Movie
Electron diffraction pattern
sand
electrons
sand
electrons
sand
Two overlapping
piles of sand
electrons
Not just two
overlapping “piles”
of electrons
sand
Two overlapping
piles of sand
electrons
Interference pattern
Photons (particles!)
water droplet
trapped atoms
 G.P. Thomson detected electron diffraction patterns by
passing a beam of electrons through a metal foil and obtaining
an interference pattern
Example 1
Find the de Broglie wavelength for an electron moving at
7.30 x 106 m/s.
Example 2
An electron is accelerated from rest by a potential difference
of 1.50 kV. Determine the de Broglie wavelength of the
electron.