De Broglie's equation

After the discovery of the photoelectric effect it was realised that waves can possess particle like properties, and a search was made to see if particles could indeed behave like waves.

In 1923 Louis de Broglie proposed that a particle of mass m travelling with a velocity v would have a wavelength l given by the equation:

l  =  h

mv

where h is the Planck constant. The intensity of the wave represented the probability of the particle being found at that point.

mv = momentum = p

therefore   l  =  h