In 1924, de Broglie delivered his thesis on "Researches on the quantum theory" to the science faculty at the Paris University. He suggested that if a light could behave as a particle then particles should be able to behave as waves. He was then convinced that the production of a wave can be associated with the motion of a particle, whether it be a photon, proton or an electron. He started by assigning a frequency to a wave that accompanied a particle through space and time; then related that wave with the motion of the particle and then actually measured the wave. de Broglie was then able to come up with a mathematical equation that described his idea about photons.
λ = wavelength (in meters)
h = Planck's constant
m = mass of moving particle (in kg)
v = velocity of moving particle (m/s)
At the time, this idea seemed very ridiculous to other scientist but it only took a couple of years to confirm de Broglie's wavelength equation theory.