De Broglie's particle/wave thoery
In the 1920's Louis de Broglie introduced a very strange concept( wave theory of matter) into physics.
He stated that all matters act like waves, and a particle's momentum(m*v)
equals planck's constant( h ) divided by the particle's wavelength ( )
Until the experimental facts were confirmed, his concepts were not accepted.
But he didn't explain why light has wave-particle duality.
De broglie's equation has a mass, its mass is not zero.
Light has wave-partilce duality, but the mass of light is zero.