1
$\begingroup$

Lets say we have an electron with known De Broglie wavelength $\lambda$. Can anyone justify or explain why we calculate its energy $E$ using 1st the De Broglie relation $\lambda = h/p$ to get momentum $p$ and 2nd using the invariant interval to calculate $E$:

\begin{align} p^2c^2 &= E^2 - {E_0}^2\\ E &= \sqrt{p^2c^2 + {E_0}^2} \end{align}

Why we are not alowed to do it like we do it for a photon:

\begin{align} E=h\nu = h\frac{c}{\lambda} \end{align}

These equations return different results.

$\endgroup$
1
  • $\begingroup$ Because of Pauli exclusion principle. $\endgroup$
    – Veeramohan
    Jul 25, 2013 at 10:59

1 Answer 1

2
$\begingroup$

Note that the equation $E=h\nu$ does not account for the energy equivalent of particle's mass. It assumes zero mass.

Photons has zero mass. You can actually substitute zero for $E_0$ so that $p^2c^2 = E^2$, and then apply de Broglie's relations so that $E = h\nu$.

$\endgroup$
2
  • 1
    $\begingroup$ False. see Matter waves $\endgroup$
    – Trimok
    Jul 25, 2013 at 12:02
  • $\begingroup$ Maybee it really has to do something with a fact that an electron has a mass... $\endgroup$
    – 71GA
    Jul 25, 2013 at 15:16

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.