Is Total Energy Always Double the Kinetic Energy in Quantum Mechanics?

[bon]

Homework Statement

Ok so (1) E = hf and (2) lambda = h/p

Homework Equations

The Attempt at a Solution

For a particle mass m, speed v, momentum p

Surely if p^2 / 2m = Ek (kinetic energy)

then we can write from (2) Ek = h^2/ 2m lambda^2

But from (1) we can write E = hv/lambda => E = h(p/m)/lambda => E = h^2 / m lambda^2

This seems to imply that for such a particle total energy is always double KE. What's gone wrong?

 

[Delphi51]

p^2 / 2m = Ek applies to ordinary particles, not photons.
Photons are WEIRD. The fact that p = h/λ applies to both is incredible and I think de Broglie thought of it while drinking beer.

 

[bon]

Yes but I am talking about an ordinary particle here..
Does E=hf not work for ordinary particles?

 

[Delphi51]

E = hf applies to photons only.