Einstein's theory on photoelectric effect

[agtee]

Hey all,
can anyone answer this question??
according t einstein's theory on photoelectric effect if the photon's energy is less then the work function of the material, electron can not come out...

My question is: what happens when a lower energy(less then work function of a material) collides with electron..?

 

[Fightfish]

I should think that most of the time, the photon is absorbed by the electron, raising the electron to a higher energy level. (since we're talking about the photoelectric effect, I guess its right to assume that the material in question has the continuous energy bands characteristic of a solid)

 

[agtee]

yaa so if lower energy photon just gives all of its energy to the electron n just befor that electron comes to its lower energy state again, another photon strikes ti electron n now its energy get higher then it should come out... is it possible?

 

[ZapperZ]

yaa so if lower energy photon just gives all of its energy to the electron n just befor that electron comes to its lower energy state again, another photon strikes ti electron n now its energy get higher then it should come out... is it possible?

What you are describing is called a multiphoton photoemission. It certainly is possible, and this technique has been used to study various materials properties.

However, the probability of this occurring is very small. The electron in the excited state has a very short lifetime (in metals, it is of the order of femtosecond). Furthermore, there has to be a photon that can excite that exact electron. This is why multiphoton photoemission processes are typically done with high powered laser, or at least, with optics that can provide a high photon density per unit area.

In any case, for the typical photoelectric effect, which is a single-photon photoemission process, Einstein's model is still perfectly valid.

Zz.

 

[agtee]

Thanks a lot for your information... my question is solved.

 

[agtee]

One more question: What made einstein state that all of the energy of the photon transfers to the electron during collision... coz there can not be head on collision?

 

[agtee]

compton effect is true but i was asking what are the factors that affects this type of collision, whether it would be head on or not; complete absorption(of energy) or not?