9702 · 22.3
Wave-particle duality — FAQ
Frequently asked questions for 9702 Wave-particle duality. Direct answers first, then deeper explanation — then practise with marking.
What is wave-particle duality and why is it important in physics?
Wave-particle duality is the concept that quantum entities, such as light and electrons, can display both wave-like and particle-like properties depending on how they are observed. It's crucial because it revolutionised classical physics, explaining phenomena unexplainable by either pure wave or pure particle models, and forms the bedrock of quantum mechanics.
How does the photoelectric effect prove the particle nature of light?
The photoelectric effect shows that electron emission from a metal depends on the light's frequency, not its intensity, and only occurs above a threshold frequency. This 'all-or-nothing' behaviour, along with instantaneous emission, strongly supports light consisting of discrete energy packets (photons) that interact one-to-one with electrons, rather than continuous waves.
Can everyday objects also exhibit wave-like properties?
Yes, according to the de Broglie hypothesis, all matter has an associated de Broglie wavelength. However, for everyday objects like a cricket ball, the mass (m) is so large that its momentum (p=mv) is also very large. Since wavelength λ = h/p, the de Broglie wavelength becomes incredibly tiny – far too small to observe any measurable wave effects like diffraction.