# Chapter 5: Wave-Particle Duality

Waves and particles each have unique properties, often properties that are mutually exclusive. But light, classically considered a wave, sometimes *behaves like* a particle (which we call a photon) and the electron, classically described as a particle, sometimes *behaves like* a wave. This chapter explores the evidence for wave-particle duality of light and electrons (as well as all other *particles*), the implications, and possible ways of understanding this duality. In the process, we also introduce and begin to explore the uncertainty principle: the position and the momentum of a particle cannot both be known precisely at the same time.

# Table of Contents

## Sections

- Section 5.1: Wave and Particle Properties.
- Section 5.2: Light as a Particle: Photoelectric and Compton Effects.
- Section 5.3: Exploring the Properties of Waves.
- Section 5.4: Wave Diffraction and Interference.
- Section 5.5: The Electron Double-Slit Experiment.
- Section 5.6: Double-Slit Experiment and Wave-Particle Duality.
- Section 5.7: Exploring the Davisson-Germer Experiment.
- Section 5.8: Diffraction and Uncertainty.
- Section 5.9: Phase and Group Velocity.
- Section 5.10: Exploring the Uncertainty Principle.
- Section 5.11: Exploring the Dispersion of Classical Waves.

## Problems

- Problem 5.1: Photoelectric effect: vary the incident light.
- Problem 5.2: Photoelectric effect experiment: vary incident light and retarding voltage.
- Problem 5.3: Compton Effect.
- Problem 5.4: Properties of a traveling wave.
- Problem 5.5: Properties of standing wave.
- Problem 5.6: Find the wavelength of the source.
- Problem 5.7: Electron diffraction.
- Problem 5.8: Davisson-Germer diffraction of electron off unknown material.
- Problem 5.9: Uncertainty principle and double slit.
- Problem 5.10: What is the de Broglie wavelength of the tennis ball?
- Problem 5.11: Phase and group velocity.