# de Broglie wavelength

Matter has a wavelength, lambda = h/p. Only tiny particles have a noticeable one.

Physics (university) · Part 10: Relativity and quantum physics · Card 7 of 11 · Last updated 2026-10-19

## Analogy

Electrons can make interference patterns like light.

## Example

**Electron wave**

lambda = h / (m v)
= 6.63e-34 / (9.11e-31 x 1e6)
= 7.3e-10 m

## In practice

An electron at 1e6 m/s has a wavelength of about 0.73 nm, similar to atom spacing.

## Practice

### Flashcards

- **What is the de Broglie wavelength?** lambda = h/p.

## Questions people ask

### Why don't we see everyday objects behave like waves?

Their wavelength is absurdly small. A 0.15 kg ball at 40 m/s has a wavelength of about 1e-34 m, far smaller than any atom, so no interference can be seen. Waves show up only for particles with tiny mass, such as electrons.

### How is it used in electron microscopes?

Electrons accelerated through thousands of volts have wavelengths below 0.01 nm, much shorter than visible light at 400 to 700 nm. Shorter wavelengths resolve smaller details, so electron microscopes can see viruses and even single atoms, which ordinary optical microscopes never can.

## Related concepts

- [Photon](https://studyvisually.com/learn/science/physics-university/physics-university-part-10/physics-university-part-10-concept-5)
- [Photoelectric effect](https://studyvisually.com/learn/science/physics-university/physics-university-part-10/physics-university-part-10-concept-6)
- [Uncertainty principle](https://studyvisually.com/learn/science/physics-university/physics-university-part-10/physics-university-part-10-concept-8)
- [Wave function](https://studyvisually.com/learn/science/physics-university/physics-university-part-10/physics-university-part-10-concept-9)

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