# Threshold Frequency: PE effect

Spastik_Relativity
In the Photoelectric effect what is the threshold frequency dependent on?
This isn't homework I was just pondering.
Is it the binding forces between the electron and the nuclues or is it dependent of a property of the photon?

Homework Helper
If it's not homework, then it should be in the homework section- I'm moving it to "General Physics".

Staff Emeritus
Spastik_Relativity said:
In the Photoelectric effect what is the threshold frequency dependent on?
This isn't homework I was just pondering.
Is it the binding forces between the electron and the nuclues or is it dependent of a property of the photon?

It depends on the atom (how many and what type of valence electron it has), the crystal structure of the material (how they are arranged when they formed the solid), and what type of solid it became (metal, semiconductor, etc).

I've repeated this many times, but in the typical photoelectric effect, you are dealing with the valence BAND from a SOLID, not individualized atom. The individual atom has lost its identity when it forms a solid since it now has to live with others of its kind. So the atomic property is gone when we deal with the typical photoelectric effect (we're not talking about X-ray photoemission here). This means you have to deal with the property of the SOLID as a whole instead.

Zz.

Spastik_Relativity
So the thresold frequency is dependent on the properties of the valency band, right?

Because i was fiddling around with waves and the idea that in the Photoelectric effect that either none or all of the momentum of the photon is transferred to the electron and i came up with a relationship between threshold frequency and teh wavelength of the photon.

It was confusing.

Staff Emeritus
Spastik_Relativity said:
So the thresold frequency is dependent on the properties of the valency band, right?

Because i was fiddling around with waves and the idea that in the Photoelectric effect that either none or all of the momentum of the photon is transferred to the electron and i came up with a relationship between threshold frequency and teh wavelength of the photon.

It was confusing.

Eh?

Your post is confusing too! It is why photoelectric effect can only occurs in solids - the lattice takes up the photon's in-plane momentum and the electron's recoil momentum! You do not get a photoelectric effect on free electron gas. Refer to any text or review on photoemission spectroscopy.

Zz.

Spastik_Relativity
ZapperZ said:
Eh?

Your post is confusing too! It is why photoelectric effect can only occurs in solids - the lattice takes up the photon's in-plane momentum and the electron's recoil momentum! You do not get a photoelectric effect on free electron gas. Refer to any text or review on photoemission spectroscopy.

Zz.

Yeah I get that it only applies for solids.
But I thought that in a photon-electron interaction either all the photons momentum or none of the photons momentum is given to the electron in the metal.
From the above principle I applied the conservation of momentum and Einstien's photoelectric equation: Energy = Threshold Energy + Kinetic Energy of Electron, and I derived a relationship between threshold frequncy and wavelength of the the photon.

Does that make sense?