# Physics - Wave-Particle Duality

> Source: https://ollybritton.com/notes/a-level/physics/topics/wave-particle-duality/ · Updated: 2021-06-09 · Tags: school, physics, waves, quantum, year-1

## See Also
- [Physics - Quantum Physics](https://ollybritton.com/notes/a-level/physics/topics/quantum-physics/)
- [Physics - The Photoelectric Effect](https://ollybritton.com/notes/a-level/physics/topics/photoelectric-effect/)

## Flashcards
##### What's the evidence that light exists as a particle??
The photoelectric effect.

##### What's the evidence that light exists as a wave??
They form diffraction patterns.

##### What's the evidence that electrons exist as a wave??
They form diffraction patterns.

##### What would you expect when firing electrons through two slits if they are a particle??
There should be two bright spots and no inteference pattern.

##### What do you get when you fire electrons through two slits??
An inteference pattern.

##### What three pieces of equipment do you need to use to demonstrate electrons can act like waves??
* Electron gun
* Thin graphite grating
* Luminescent screen

##### What happens for the fringe spacing in a diffraction pattern created by fast-moving electrons??
It is small.

##### What happens for the fringe spacing in a diffraction pattern created by slow-moving electrons??
It is large.

##### What is the formula for the de Broglie wavelength $\lambda$ of a particle with mass $m$ and velocity $v$??
$$
\lambda = \frac{h}{mv}
$$

##### What's another way of thinking about the de Broglie wavelength in terms of momentum??
$$
\lambda = \frac{h}{\text{momentum}}
$$

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