Wave Particle Duality

Light behaves as a particle in the photoelectric experiment, but it behaves as a wave in diffraction/interference of light.

For particles, there are also particle and wave properties.

You can calculate the wavelength of a particle by using $\lambda = \frac{h}{p}$

Derivation of the above equation:

Using E=mc2 and E=hf,

$$\begin{aligned} mc^{2} &= hf \\ mc &= \frac{hf}{c} \end{aligned}$$

Momentum of a photon is p = mc, hence $p = \frac{hf}{c}$.

$$\begin{aligned} p &= \frac{hf}{c} \\ &= \frac{h}{\lambda} \end{aligned}$$

It has been shown experimentally that electron undergoes diffraction when directed through a thin metal foil.

It has been found that both the wave and particle aspects cannot be revealed simultaneously in a single experiment.