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Name: Anthony
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Question:
I know what the photoelectric effect is, but everything I have read only talks about metals. Can the photoelectric effect occur on other substances, such as water?



Replies:
Non metals are not likely to exhibit any photoelectric effect, because only metals have 'spare' electrons available in their outer shells. It is those 'spare' electrons which are able to be dislodged by the occasional passing photon provided that the photon has sufficient energy. The energy of the photon is determined by the frequency of the radiation - and that also determines the colour if it is visible light - blue having more energy than red. Given all that, some non metals - mostly in the metalloid group - can exhibit weak photoelectric effects if the energy of the impeding photons is high enough - X-rays and so on. Covalent compounds- such as water - are MUCH less likely to show any photoelectric effect, because the electrons are all neatly paired off and bound up in shared electron shells and so on. Not much chance of knocking an electron out of there.

Nigel Skelton
Tennant Creek AUSTRALIA


In principle yes. However, the energy required to remove an electron from a non-conductor is much greater than is required to remove the electron from a metal, so for practical purposes, only metals are easy to remove the conducting electrons.

Vince Calder


Anthony,

The photoelectric effect can occur with any material, but it will seldom be seen enough to be noticed. For a metal, there are electrons moving through the metal, not joined to a specific atom. These electrons are easy to knock free from the material. The photoelectric effect happens often. With atoms that hold their electrons tightly, a photon is much less likely to knock an electron free. Also, greater energy is needed to make it happen. This means a higher energy photon, perhaps x-rays, rather than visible light. Photoelectric effect can still happen in non-metals, but it is much easier to make happen for a metal.

Dr. Ken Mellendorf



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