Why Does One Photon of Light Cause the Emission of One Electron?

[dev70]

hi pf, while reading photoelectric effect i found that one photon of light causes the emission of one electron? I want to know why?

 

[tiny-tim]

hi dev70!

are you asking about the number?

one photon can certainly cause the emission of zero electrons (it usually does! )

so far as i know, it can also cause the emission of two or more electrons (if it has enough energy), but i suspect the probability of that is fairly low

 

[dev70]

as far as i know or i searched in the web i found in many sites saying that one electron can absorb the energy of one photon or somewhat similar to what i asked. i want to know how and why?

 

[tiny-tim]

as far as i know or i searched in the web i found in many sites saying that one electron can absorb the energy of one photon or somewhat similar to what i asked. i want to know how and why?

i'm not following what's worrying you about this

a photon has a certain amount of energy

if it hits an atom, the energy of the photon can be absorbed by one of the electrons in the atom …

if that photon energy is less than the "binding energy" of the electron, then the energy is just released again, and the photon is re-emitted

but if the photon energy is more than the "binding energy" of the electron, then the electron can absorb the energy, and escape from the atom, with a kinetic energy equal to the difference between the photon energy and the electron's "binding energy"

have you read http://en.wikipedia.org/wiki/Photoelectric_effect#Emission_mechanism ?

is there any particular part of it you don't follow?​

 

[dev70]

No, i think i got it. Thank you

 

[gema]

Do you dev70? I have the same question too
Can you share me why?

 

[tiny-tim]

hi gema!

which part of it you don't follow?​

 

[gema]

Hi tim-tim
why only one photon can be absorb by one electron?
I really am confuses.

 

[tiny-tim]

the probability of two photons hitting the same electron at the same time is negligible

so if no photon has enough energy to release the electron on its own, the electron won't be emitted

 

[gema]

thanks tiny-tim

 

[dev70]

yesterday in an exam i got a question on photoelectric effect.
will there be emission of electrons if the energy of incident wave is exactly equal to work function?

 

[tiny-tim]

yesterday in an exam i got a question on photoelectric effect.
will there be emission of electrons if the energy of incident wave is exactly equal to work function?

hmm … looks like a catch question

i'll guess that the thermal motion means that half of the atoms must be moving away from the light source, which will be red-shifted, so they won't receive enough energy (but the other half will)

but i don't know what the official answer is