Wave-particle duality
Light does not behave exclusively as a wave or a particle, it exhibits characteristics of both. This concept is known as wave–particle duality, and it is fundamental to quantum physics.
In many situations, light behaves like a wave. It can refract, reflect, diffract, and polarise, and it can undergo interference, producing patterns of constructive and destructive superposition.
In other contexts, light behaves like a particle. It has momentum, is quantised, and transfers energy in discrete packets called photons. This particle-like nature was crucial in explaining the photoelectric effect, for which Albert Einstein was awarded the Nobel Prize. The effect revealed that only photons above a certain energy threshold could eject electrons from a metal surface—something the classical wave model could not account for.
This dual nature of light, that it exhibits both wave-like and particle-like behaviour, is central to modern physics. This duality is essential for understanding quantum phenomena.
This resource revises particle-wave duality and within particle-wave duality there are 3 key concepts:
To determine if this resource will benefit you, start by answering the following questions.
- Why does light exhibit wave-like properties for some experiments but acts like a particle for others?
- Can particles act like waves and can waves act like a particle?
- If you were put in a room with Maxwell, Einstein, Planck, Young and asked what is light would they be able to agree on an answer? What about matter?
The answers to these questions are provided on the following pages. Use this resource to refresh your memory, reinforce your understanding of these concepts, and prepare more effectively for university-level learning.