Energy-momentum relation
E2 = p2c2 + m2c4
E = mc2 if p=0
E = pc if m=0
Rest energy
photons
E = p2/2m non-Rel KE
Electrons (non-Rel)
de Broglie
 = h/p
Light
Waves
Photo effect
Photons
f = c
f = c/
E = h f = h c/
E = (h/2 )(2 f)
E = pc
p = h/
f = c
 = 2 f
k = 2/
/k = f  = c
approximate
(electron)
Energy-momentum relation
E2 = p2c2 + m2c4
E = mc2
E = pc
if p=0
if m=0
Light
E=p2/2m
non-Rel KE
Electrons (non-Rel)
f = c
Photo effect E = h f = hc /
Waves
de Broglie
Photons
E = pc
 = 2 f k = 2/
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