## kinetic energy of electron

George_Zhu
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Joined: Mon Jun 17, 2019 7:23 am

### kinetic energy of electron

When will the electron has zero kinetic energy?

Jeril Joseph 1B
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Joined: Mon Jun 17, 2019 7:23 am
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### Re: kinetic energy of electron

Well, there'd only be 0 kinetic energy for an electron when the energy of a photon is equal to the energy needed to remove an electron. So, refer to the E(photon)-E(work function)=E(excess). The excess energy is the kinetic energy. But the kinetic energy would be 0 when the photon's energy is at the absolute minimum needed to release an electron from a substance.

hannabarlow1A
Posts: 37
Joined: Mon Jun 17, 2019 7:23 am

### Re: kinetic energy of electron

When the energy of the photon is equal to the threshold energy (energy needed to release an electron), then kinetic energy of the electron will equal 0. If the photon's energy was less than the threshold energy, an electron would not be released, and if the photon's energy was greater than the threshold energy, kinetic energy would be greater than 0.

Brian Kwak 1D
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Joined: Fri Sep 28, 2018 12:17 am

### Re: kinetic energy of electron

When the energy of light(photon) is equal to the work function(threshold energy). For me it’s easier to think of it in terms of the law of conservation of energy and the equation: energy of light(photon) = threshold energy(work function) + kinetic energy of electron(excess energy in the form of kinetic energy). Conceptually If the energy is equal to the threshold energy then there will be no electron ejected so there will be no kinetic energy. An electron can only be ejected when the energy of the photon is greater than the threshold energy.

David Zhang 1B
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Joined: Mon Jun 17, 2019 7:23 am

### Re: kinetic energy of electron

There is only a certain amount of energy in a photon. If there is more energy than is needed to release the electron, then the extra energy is kinetic. If the energy to release the electron is the exact same as the photon, then there is 0 kinetic energy.

Chris Charton 1B
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Joined: Mon Jun 17, 2019 7:23 am

### Re: kinetic energy of electron

How can something be released with a KE of 0? That would mean it has no velocity, so its position would not change.

Posts: 36
Joined: Mon Jun 17, 2019 7:23 am

### Re: kinetic energy of electron

I think kinetic energy is the energy left from the photon left over after taken into account the work function. In class I think he said that electrons can be ejected if the energy of the photon is equal to or greater than the energy needed to remove an electron. However, if it is equal to then the kinetic energy (left over energy) would be 0.

Daniel Kim 1D
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Joined: Wed Oct 03, 2018 12:17 am

### Re: kinetic energy of electron

When the E (energy of the photon) equals the work function. Kinetic energy = energy of photon - work function

somyapanchal1D
Posts: 34
Joined: Mon Jun 17, 2019 7:23 am

### Re: kinetic energy of electron

An electron will have zero kinetic energy (Ek) when there is no excess energy left over from the photoelectric effect. Look at the equation below:

E(photon)-E(remove an electron)=E(excess) OR
E(photon)-(work function)=Ek

When we set Ek equal to zero, the equation becomes:

E(photon)=E(remove an electron) OR
E(photon)=(work function)

Thus, kinetic energy will equal zero when the energy of a photon that shines on a metal surface matches the amount of energy required to remove an electron. If the energy of a photon is equal in value to the energy needed to remove one electron (also known as threshold energy), then the kinetic energy will be zero. This means that there will be no excess energy left, but the electron will still be ejected from the surface.