The Davisson-Germer experiment verified the de Broglie hypothesis that matter has wave-like properties. They directed electrons onto a nickel crystal target and detected the scattering angle and intensity of the electrons. By comparing the scattering to X-ray diffraction experiments, they determined the wavelength of the electrons. This matched the wavelength predicted by de Broglie's equation for matter waves, providing direct evidence that electrons behave as waves. This experimental confirmation established that all matter has both particle-like and wave-like properties.

1. Davisson-Germer
Experiment

2. de Broglie hypothesis
Photons:

h
ph 
E
Wave → Particle

h
k
p 
 
What about the opposite?
Particle → Wave ?
p
h



3. de Broglie hypothesis
Matter waves:
mK
h
mv
h
p
h
B
2




Wavelength for a walking man?
Wavelength for a moving electron?
How to reveal the wave properties of electrons?
What is the wavelengths difference for 5 eV electron
and 5 eV photon?

4. Experimental verifications
X-rays diffraction:
X-rays are electromagnetic waves with
λ = 10-8 to 10-12 m = 10 – 0.001 nm

5. Experimental verifications
Bragg’s law:

 n
d 
sin
2
If θ and λ are known,
d can be determined

6. Experimental verifications
Davisson-Germer experiment:
• Electrons were directed
onto nickel crystals
• Accelerating voltage is
used to control electron
energy: E = |e|V
• The scattering angle
and intensity (electron
current) are detected
– φ is the scattering angle

7. Experimental verifications
Electron scattering:
From X-ray
experiments:
d = 0.091 nm
For φ = 50°
(θ = 65°):
λ = 0.165 nm

 n
d 
sin
2

8. Davisson-Germerexperiment
• Application of diffraction to measure
atomic spacing
• Single crystal Ni target
• Proved deBroglie hypothesis that
λ=h/p

9. Proof that λ=h/p
Accelerated electrons have energy eV:
eV= ½ mv2 => v = (2Ve/m)1/2
de Broglie said:
λ=h/p=h/(mv)=h/(2mVe)1/2=1.67 Å
Davisson-Germer found lattice spacing: λ=dsinθ=1.65 Å
Excellent agreement between theory and experiment!

10. Application: Pressure sensing
• Atomic spacing changes with pressure:
Pressure=E(ΔL/L)
Where E=Young’s modulus (N/m2)
• As d (spacing between atomic planes) changes, the angle of
diffraction changes
• Diffraction rings move apart or closer together