Wave-Particle Duality
Physics: AQA A Level, topic 12.2.4
De Broglie Hypothesis
De Broglie suggested particle-wave duality in his PhD thesis.
Light as a wave
- Light has properties which show that it behaves as a wave.
- Light can produce interference patterns.
- Light can be diffracted.
Light as a particle
- Light also has properties which show that it behaves as a particle:
- The photoelectric effect is explained using a particle model.
De Broglie's hypothesis
- De Broglie suggested particle-wave duality.
- He suggested that all particles can behave as a wave, and all waves can behave as particles.
- He linked the two with his equation for the de Broglie wavelength:
- .
Electron Diffraction
If de Broglie's hypothesis is correct, then particles such as electrons should show effects such as diffraction.
Electrons as a wave
- Following de Broglie’s hypothesis, many people wanted to find evidence of the electrons as a wave.
- Electron diffraction was the first successful attempt.
Electron diffraction
- When electrons are accelerated through a vacuum tube and interact through space in a graphite crystal, they can form an interaction pattern.
Diffraction pattern
- The electron diffraction pattern has a bright central disc, and circular bands around it.
- As the electron speed increases, the pattern gets tighter.
Test yourself on Wave-Particle Duality
Which of the following is explained by viewing light as a particle?
Which is the correct formula for the de Broglie hypothesis?
What was the first piece of experimental evidence that electrons behave as waves?
Electron Diffraction Experiment
Which of these statements are true about electron diffraction?