Einstein In 1905 Einstein showed that the photoelectric effect could be understood if light were thought of as a stream of particles (photons) with energy equal to hf. I got my Nobel prize for that.
Louis de Broglie (in 1923) If light can behave both as a wave and a particle, I wonder if a particle can also behave as a wave?
Louis de Broglie Ill try messing around with some of Einsteins formulae and see what I can come up with.
I can imagine a photon of light. If it had a mass of m p, then its momentum would be given by p = m p c where c is the speed of light.
Now Einstein has a lovely formula that he discovered linking mass with energy (E = mc 2 ) and he also used Plancks formula E = hf. What if I put them equal to each other? mc 2 = hf
So for my photon m p = hf/c 2 So if p = m p c = hf/c
p = m p c = hf/c Now using the wave equation, c = fλ (f = c/λ) So m p c = hc/λc = h/λ λ = h p
So youre saying that a particle of momentum p has a wavelength equal to Plancks constant divided by p?! Yes! λ = h/p It will be known as the de Broglie wavelength of the particle
Confirmation of de Broglies ideas De Broglie didnt have to wait long for his idea to be shown to be correct. In fact in 1929 I received a Nobel prize for my prediction of the wave nature of the electron.