1. Module 6

1.16. Page 5

Lesson 3

Module 6—Wave-Particle Duality and Quantum Physics

 

Lesson Summary

 

In this lesson you focused on the following questions:

  • What is the Compton effect and how is it related to the conservation of energy and momentum?
  • How does the Compton effect support wave-particle duality?
  • If light can behave as a particle, can a particle behave as a wave?
  • What is de Broglie’s wave equation?

The Compton effect is an increase in wavelength, hence a decrease in energy, of an X-ray as a result of its interaction with matter. Compton observed the energy and momentum of the incident X-ray, the scattered X-ray, and the electron it collided with. He discovered that the collision demonstrated the conservation of momentum and energy, just as it would for an elastic collision between two particles. Thus, the Compton effect provides supporting evidence for the particle nature of EMR.

 

The de Broglie wave equation is based on the Compton effect and predicts that any particle that possesses momentum will have a characteristic wavelength according to . If correct, his prediction would show that a moving particle exhibits wave-like properties. His prediction was verified by the electron wave interference, accidentally observed by Davisson and Germer who received the Nobel Prize for the discovery of “matter waves” in 1937. The de Broglie wave equation also explains the quantization of electron energy using resonance and wave interference in a confined space.

 

Lesson Glossary

 

Compton effect: an increase in wavelength of an X-ray as a result of its interaction with matter

 

Compton scattering: the scattering of an X-ray when it interacts with an electron

 

Heisenberg’s uncertainty principle: a principle stating that it is impossible to know both the position and momentum of a particle with unlimited precision at the same time