## Energy of Photon [ENDORSED]

Ryan Neis 2L
Posts: 53
Joined: Fri Sep 29, 2017 7:04 am

### Energy of Photon

I know that the energy of a photon has to be greater than the energy to remove an electron in order for light to be absorbed, but what happens when the energies are equal to each other? Is there a difference in outcome or in the values of the velocity of the electron?

David Minasyan 1C
Posts: 54
Joined: Thu Jul 13, 2017 3:00 am

### Re: Energy of Photon  [ENDORSED]

From what I know (and if someone would confirm) if the energy of the photon equals the amount of energy to eject the electron then that electron is ejected with a 0 kinetic energy.

Michelle Dong 1F
Posts: 110
Joined: Fri Sep 29, 2017 7:04 am

### Re: Energy of Photon

The kinetic energy is the "excess energy," so there would be no excess energy to remove the electron from the metal.

Elika Asis 3C
Posts: 19
Joined: Fri Sep 29, 2017 7:07 am

### Re: Energy of Photon

Since the equation for kinetic energy is E(photon) - E(energy required to remove e-) = E(excess) = Ek, if the energy of the photon would cancel out the threshold energy/work function and it would lead the kinetic energy to equalling zero. So, the electron would be emitted with Ek = 0!
Hopefully that helps a little bit

Posts: 23
Joined: Fri Sep 29, 2017 7:05 am
Been upvoted: 1 time

### Re: Energy of Photon

This would mean that the kinetic energy is equal to 0. Kinetic energy is something that is considered excess in the energy equation involving the photon, and if the kinetic energy is equal to 0 then that would be the maximum wavelength of that photon as well.

aaron tang 2K
Posts: 49
Joined: Thu Jul 27, 2017 3:01 am

### Re: Energy of Photon

When the energy is equal to each other, the energy is still enough to emit a photon, but the kinetic energy would be zero.

Sarah Brauer
Posts: 17
Joined: Fri Sep 29, 2017 7:06 am

### Re: Energy of Photon

Would light be emitted with zero kinetic energy?

Ramya Lakkaraju 1B
Posts: 67
Joined: Fri Sep 29, 2017 7:03 am

### Re: Energy of Photon

Yes, if the energy of the photon exactly matches the work function of the metal, the electron that is emitted will have zero kinetic energy.

Jean Mok 3K
Posts: 22
Joined: Sat Jul 22, 2017 3:01 am

### Re: Energy of Photon

If the energy of the photon is exactly equal to threshold energy, or "the energy [required] to remove an electron" as you put it, then the electron is ejected. However, because all of the energy was consumed as work, there is no more energy to translate into kinetic energy, thus the velocity of the ejected electron would be zero. I hope this answered your question!

Michelle Lu 1F
Posts: 50
Joined: Thu Jul 27, 2017 3:01 am
Been upvoted: 1 time

### Re: Energy of Photon

I know that the energy of a photon has to be greater than the energy to remove an electron in order for light to be absorbed, but what happens when the energies are equal to each other? Is there a difference in outcome or in the values of the velocity of the electron?

Yes, when the energy of the incoming photon is greater than the threshold energy (defined as the energy to remove an electron from that surface), then the difference between these two energy values is the kinetic energy of the electron released. Thus, when the energies are equal, this merely means that the kinetic energy of the ejected electron is 0 J.