Matter Waves (Wave Particle Duality)

Special relativity said that

[math]\displaystyle{ E = pc }[/math] if m=0

Plank said he could fit the Black Body radiation data assuming that that

[math]\displaystyle{ E= hf }[/math] where [math]\displaystyle{ h = 6.63 \times 10^{-34} \mbox{ J} \cdot \mbos{s} }[/math] = Plank's constant

Combining the two we have

[math]\displaystyle{ p=\frac{E}{c} = \frac{ h f}{c} }[/math]

[math]\displaystyle{ \Rightarrow }[/math] photons have momentum like a particle (mv)

Davisson and Germer

From hyperphysics: