photoelectric effect

Physicsissuef

Is in the photoelectric effect, the electrons are oppositing the electromagnetic field or they are excited from the energy?

mathman

I don't understand your question. However, the photoelectric effect involves an electron absorbing a photon and, being more energetic, leaving the atom.

Physicsissuef

And do ultraviolet radiation pass to the metal, or just visible light?

ZapperZ

You really need to put a bit more effort in asking your question here, expecially if you want others to put effort into responding. If not, you will continue to get responses from other people in the form of "HUH?", and you will have to keep on explaining yourself.

UV radiation can cause photoemission if the work function is below the photon energy. Now what is it exactly that you want to know here in this thread?

Zz.

Physicsissuef

Ok, sorry. I just want to know, if UV radiation passes through the glass bulb, the glass will absorb that energy. So what is causing the electrons to flow? UV radiation or visible light, or maybe something else?

ZapperZ

This is getting utterly confusing. You WERE asking about the photoelectric effect, weren't you? Why is it optical conductivity now?

Glass bulb? When did that come in? Did you mention about glass anywhere till now? There's no "photoemission" using UV source on glass bulb, is there?

Why don't you start from the very beginning and ask your question once again. But this time, please put in as much effort and information in your question so that we know (i) what you know (ii) what exact it is the picture that you have in your mind. If you see that you have to ADD new stuff as you go along, it means clearly that you omitted important information in your original question.

Zz.

Physicsissuef

Sorry for being rude, but have you ever heard about photoelectric tube or photoelectric cell? There is glass balloon or bulb or whatever... Inside there is vacuum, so it is called vacuum photocell. There are anode and cathode. So when I bring some kind of radiation to some metal, the electrons are excited and pulled off the cathode. What is that kind of radiation? UV or visible light? Also I want to know why the anode and cathode are put in vacuum photocell?

mathman

The vacuum is used so the electrons can stream without interacting with anything. The radiation is always electromagnetic, as long as the frequency is high enough to excite the electrons of the material being used.

ZapperZ

Not only have I heard of them, I've used them!

What kind of radiation? Any radiation in which the photon energy is higher than the work function! I thought I mentioned this already.

Electrons do not travel very far in air, and even if they do, a lot of them get scattered off and would not reach the anode. This is not what you want when you are using a photocell to detect EM radiation. If you are trying to detect UV, the "glass" has to be either quartz or fused silica, because ordinary glass absorbs UV.

Zz.

Physicsissuef

Ok, thanks. I understand now. I have two more questions. Why the cathode and anode are in vacuum balloon instead connected them with wire? Is this picture correct?

ZapperZ

If they are connected to a wire, they would be the SAME thing, not two different things. The anode has to be at a higher potential then the cathode, the latter is usually grounded.

Zz.

Physicsissuef

And why in my text book says, that the kinetic energy of the electrons doesn't depends from the intensity of the radiation?

ZapperZ

Because "intensity" only increases the number of photons, not the energy within each photon.

Your textbook doesn't explain this? Please read for example, this:

http://www.colorado.edu/physics/2000...oelectric.html

Zz.

Physicsissuef

And what makes the current stronger? The more electrons ejected, or the speed of the electrons?

ZapperZ

<scratching head>

This is not clear?

Zz.

Physicsissuef

Yes, I understand that with the intensity. Thank you very much. There is one more thing in my text book. It says that the current is much stronger when I increase the intensity. So that means that more electrons are ejected and the current is getting stronger, right?

Hootenanny

Correct.