## Learning Objectives

Explain how the double slit experiment demonstrates wave-particle duality at the quantum scale.

## Prior Knowledge and Skills

3.3 Wave Behavior

## Key Terms

• Quantum scale
• Wave-particle duality
• Double slit experiment
• Photon

## Guided Inquiry

Watch these two videos which demonstrate the double slit experiment:

Wave-Particle duality, Part 1: https://youtu.be/fAVPRDnzSpE

Dr Quantum – Double Slit Experiment: https://youtu.be/DfPeprQ7oGc

Please note that electrons are used in this experiment, but the same principle will apply to light (photons).

3.6.1 Why does the double slit experiment predict two lines of intensity on the detector, if the electrons are behaving like particles?

3.6.2. Why does the double slit experiment predict multiple lines of intensity on the detector, if the electrons are behaving like waves?

Concept Check 3.6.1 The videos show the “scientific observation” as an eye.  In reality, we can’t see individual electrons.  Can you think of a way to detect electrons as they pass through the first or second slit?

Watch this video about photons:

Photon Energy | Physical Processes | MCAT | Khan Academy: https://youtu.be/Zqt3btS1FwE

3.6.3. What is a photon?

3.6.4 How is the energy of a photon related to its frequency? (note: frequency is represented by “f” in the Khan Academy video, but frequency is more often represented by the Greek letter ν “nu.”)

Summary

Light has both wave and particle-like properties.  Light can be described using wavelength or photon energy.

If you would like to explore this topic further, please see additional references below.

References

Brad Cameron. Dr Quantum – Double Slit Experiment. September 13, 2006. https://youtu.be/DfPeprQ7oGc

Bozeman Science. Wave-Particle duality, Part 1. May 29, 2014.  https://youtu.be/fAVPRDnzSpE

Khanacademymedicine. Photon Energy | Physical Processes | MCAT | Khan Academy. July 9, 2014. https://youtu.be/Zqt3btS1FwE

The Feynman Lectures on Physics, Volume I. Mainly Mechanics, Radiation, and Heat. Chapter 37. Quantum Behavior. http://www.feynmanlectures.caltech.edu/I_37.html

The Feynman Lectures on Physics, Volume III. Quantum Mechanics. Chapter 1. Quantum Behavior. http://www.feynmanlectures.caltech.edu/III_01.html