## if KE is 0 how can the electron be ejected?

kendal mccarthy
Posts: 109
Joined: Wed Nov 14, 2018 12:22 am

### if KE is 0 how can the electron be ejected?

How is the electron ejected if the energy of the photon is equal to that of the work function, meaning it has no KE? Because wouldn't it not be able to move if it has 0 KE?

Noah Canio 3C
Posts: 55
Joined: Wed Sep 18, 2019 12:20 am

### Re: if KE is 0 how can the electron be ejected?

If I remember correctly, Dr. Lavelle explained that the detector used to measure the kinetic energy of the ejected electron has a slight positive charge. This means that even if the electron is hit with an energy equal to the threshold needed (the work function), the electron will move slightly away. I don't particularly remember the minute details behind this, so if anyone can correct me if I'm wrong, then that would be greatly appreciated.

Bryce Ramirez 1J
Posts: 120
Joined: Sat Aug 24, 2019 12:16 am

### Re: if KE is 0 how can the electron be ejected?

For an electron to be ejected, the work function just has to be equal to the to the amount of energy that was used when being put on the metal. I still think that there will be a slight positive charge, but it would be negligible to calculate it. For the formula, KE would equal 0 and you would be left with E = work function, which could be simplified to h * v = work function.

Jessa Maheras 4F
Posts: 121
Joined: Fri Aug 02, 2019 12:16 am

### Re: if KE is 0 how can the electron be ejected?

I agree with the above two responses - I believe that the word "ejected" simply means liberated from the atom. The slightly charged detector can account for the additional movement.

Posts: 58
Joined: Thu Jul 25, 2019 12:15 am

### Re: if KE is 0 how can the electron be ejected?

kendal mccarthy wrote:How is the electron ejected if the energy of the photon is equal to that of the work function, meaning it has no KE? Because wouldn't it not be able to move if it has 0 KE?

If there is 0 KE, it means that there was just enough energy for the electron to escape the surface of the solid metal. 0 KE refers to the fact that the electron is not driven outward with any additional kinetic energy but simply liberated from the metal.