# De broglie vs classical wavelength

since it is defined (from what i can tell) as h/p,

is it interchangeable with the classical wavelength in equations involving waves in general? or is it a special separate case for matter?

that is,

for photons we have the following equation:
E = hf
E = hc/λ

can the same equation be used to find the wavelength/energy of electrons?

The de Broglie wavelength is now kinda viewed as the characteristic "size" of a quantum particle. It's not really a super-relevant physical quantity anymore, nor can you just put it into classical wave equations to get anything physical.

Meir Achuz
Homework Helper
Gold Member
since it is defined (from what i can tell) as h/p,

is it interchangeable with the classical wavelength in equations involving waves in general? or is it a special separate case for matter?

that is,

for photons we have the following equation:
E = hf
E = hc/λ

can the same equation be used to find the wavelength/energy of electrons?
For a photon E=pc, so the dB wavelength for a given energy is simple.
For an electron p=\sqrt[{E^2/c^2-m^2}, so the dB wave length in terms of energy is more complicated,.

For a photon E=pc, so the dB wavelength for a given energy is simple.
For an electron p=\sqrt[{E^2/c^2-m^2}, so the dB wave length in terms of energy is more complicated,.

we must include the rest mass of the electron?

jtbell
Mentor
Yes. And to get the frequency of the wave via E = hf, you must use the total energy (kinetic energy plus rest energy).

According to de broglie relation lambda=h/mv ...which implies that velocity is inversely proportional to wavelength. But According to the reletion

V=n lambda ... velocity is directly proportional to wavelength...... How That diffenence is Causesd ? Am i going wrong Somowhere ?

Hootenanny
Staff Emeritus