Wave–Particle Duality
Light and matter show both wave and particle behavior.
About this topic
Light behaves as a wave in interference and diffraction, yet as particles (photons) in the photoelectric effect. De Broglie proposed that matter also has wavelength λ = h/p, confirmed when electrons produced diffraction patterns. Everyday objects have tiny wavelengths, so their wave nature goes unnoticed.
For example, a 0.15 kg ball at 40 m/s has a wavelength of about 10⁻³⁴ m, far smaller than an atom, while an electron accelerated through 100 V has about 0.12 nm, similar to atomic spacing, so crystals can diffract electrons. In the double-slit experiment even single electrons build up an interference pattern.
Neither the wave nor particle picture alone is complete; quantum objects show whichever aspect the experiment measures. Electron microscopes exploit electron waves for sharper images than light microscopes allow.
Students sometimes think a photon is a tiny ball wiggling along a wave. It is better to see it as a quantum object whose behaviour only looks like waves or particles in particular situations.
Key ideas
- Photons carry energy hf
- Electrons diffract
- de Broglie wavelength λ = h/p
Quick check
Use cases: where Wave–Particle Duality helps
- Homework: review the key idea behind Wave–Particle Duality before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Wave–Particle Duality without notes.
- Visual learning: play with the interactive lab to see how Wave–Particle Duality changes when you adjust its inputs.
- Teaching a friend: explain Wave–Particle Duality in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Wave–Particle Duality?
Light and matter show both wave and particle behavior.
What will I learn in Wave–Particle Duality?
Photons carry energy hf. Electrons diffract. de Broglie wavelength λ = h/p.
Is Wave–Particle Duality part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Wave–Particle Duality lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Wave–Particle Duality?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.