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# Why doesn't intesnity cause a photoelectron to be emitted? watch

1. Suppose I shone red light at a metal for until the end of time.

Using the photon model, the number of photons hitting the surface of the metal at a given time increases. Each photon has a discrete amount of energy.
The frequency of red light is below the threshold frequency. So a photoelectron won't be emitted.

So far so good.

But, if the free electrons gain energy of hf when it absorbs an electron, and the red light in this situation goes shines on the meal forever wouldn't it eventually give the electrons enough energy to exceed the work function an leave the metal?

So wouldn't the energy absorbed by the electrons add up?
Also, why doesn't intensity cause a photoelectron to be emitted in insufficient frequencies of light?
Where have I screwed up in my understanding?
2. (Original post by Kushala Daora)
Suppose I shone red light at a metal for until the end of time.

Using the photon model, the number of photons hitting the surface of the metal at a given time increases. Each photon has a discrete amount of energy.
The frequency of red light is below the threshold frequency. So a photoelectron won't be emitted.

So far so good.

But, if the free electrons gain energy of hf when it absorbs an electron, and the red light in this situation goes shines on the meal forever wouldn't it eventually give the electrons enough energy to exceed the work function an leave the metal?

So wouldn't the energy absorbed by the electrons add up?
Also, why doesn't intensity cause a photoelectron to be emitted in insufficient frequencies of light?
Where have I screwed up in my understanding?
To anyone who has the same issues.

I've found out that, the energy absorbed is converted into a photon which is emitted.
3. Energy cannot be added up by the photons as when a photon gives energy to an electron they only have a one to one interaction. So if the energy of the photon does not match that which requires the electron to be released, the photon is simply not absorbed by the electron.
Energy cannot be added up by the photons as when a photon gives energy to an electron they only have a one to one interaction. So if the energy of the photon does not match that which requires the electron to be released, the photon is simply not absorbed by the electron.
I'm sure it does....

I thought, the energy turns into heat and the photons are remitted simultaneously. Please elaborate because this bit is crucial to fill the gaps in my understating.
5. Have you done excitation and dexcitation and energy levels in atoms
Have you done excitation and dexcitation and energy levels in atoms
So what e=hf?
Yes I have. Oh, okay I see. Thank you!

But why does the metal heat up if the energy isn't absorbed?
7. Energy can be absorbed and cause heating regardless of the frequency of the photons but can only result in the emission of a photo electron IF an individual photon has more than a certain energy (equivalent to the work function).

FWIW the fact that the energy can't build up over time is taken as evidence of the particle behaviour of light, as if we treat light purely as a wave, we might indeed expect the energy to build up over time and allow an electron to be released.

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