# The photoelectric effect

## Homework Statement

When monochromatic light is incident on a metla plate,electrons are emmited only when the frequency of light exceeds a certain frequency.
Explain in terms of energy, why this threshold frequency exist and why photon theory of light provides a better explnation of the photorlrctric effect than a wave theory of light.

## Homework Equations

none that i know of

## The Attempt at a Solution

Its not really a solution but i have talked about energy levels and in atoms and things like that.

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Redbelly98
Staff Emeritus
Homework Helper

## Homework Equations

none that i know of
The equation for the energy of a photon would definitely be relevant.

what E=hf or do you want the photoelectric equartion and how do either of them prove it
fh=workfunction+Ek(max)

Redbelly98
Staff Emeritus
Homework Helper
Yes, those equations.

What can you say about Ek if hf is less than the work function?

so what you are suggesting is me saying look at the formula it gives you proof?
sorry but i am not sure that will fly

Redbelly98
Staff Emeritus
Homework Helper
No, I'm not suggesting you say "look at the formula" as your answer. I'm suggesting that you should look at the formula and think about it before coming up with your answer. Ek(max) = hf - workfunction​

What would hf < workfunction imply about Ek?

I get that it says a minimum frequency is required and there is a maximum enrgy required but you have failed to prove this bit which is my hardest

why this threshold frequency exist and why photon theory of light provides a better explnation of the photorlrctric effect than a wave theory of light.

rock.freak667
Homework Helper
Well if we use wave theory, then no matter the frequency, as long as the light supplies energy eventually, the electrons should gain enough energy to be emitted. But this doesn't occur in practice.

Well if we use wave theory, then no matter the frequency, as long as the light supplies energy eventually, the electrons should gain enough energy to be emitted. But this doesn't occur in practice.
oh my god thankyou i didnt know that and thats all i wanted to here that solves my whole problem.