# What is the wave particle duality of light?

Our best understanding of light is that we must understand that light has both wave and particle properties.

Light travels as a wave. We can determine the properties of light using the following relationship

Speed = wavelength x frequency

Speed of light = 3.0 x ${10}^{8}$ m/s (this can change slightly depending on what material light is traveling through)

Wavelength = distance from crest to crest of a wave (normally measured in nanometers)

Frequency = how many wave cycles pass a fixed point in 1 s (unit of 1/s or Hertz - Hz)

We also understand that light consists of particles called photons. This is important for understanding the phenomena of atomic spectra and the photoelectric effect.

When electrons move from higher energy levels to lower ones, a photon of light is created that matches the amount of energy of the quantum leap made by the electron. We see evidence of these photons when performing a flame test experiment, watching fireworks or looking at neon lights.

When photons strike certain materials (Si for example) they can cause electrons to be removed from their orbitals. A solar cell takes advantage of this to create a flow of electrons through a circuit (electric current).