## Photons and electrons

Selena Yu 1H
Posts: 108
Joined: Fri Aug 09, 2019 12:16 am

### Photons and electrons

I was wondering how do you know the right wavelength to have the electrons ejected. How do we figure out the right wavelength? Is there an equation for that?

Jacey Yang 1F
Posts: 101
Joined: Fri Aug 09, 2019 12:17 am

### Re: Photons and electrons

We would use the equation λ = hc/E, which is derived from taking λv = c and rearranging it in terms of v, then plugging it into the Einstein equation E = hv.

Tai Metzger 3K
Posts: 103
Joined: Sat Aug 24, 2019 12:17 am

### Re: Photons and electrons

For an electron to be ejected, it must be hit with a photon that has enough energy (high enough frequency). This amount of energy is called "work function" and will generally be given in photoelectric question unless you are asked to solve for the work function. For problems like these, you should use conservation of energy: E(photon) - Work Function (energy required to eject the e-) = E(excess) = Kinetic Energy of the ejected e-.
Additionally, use E= h*frequency to find the energy of the photon.

Mellanie Gamero 4D
Posts: 10
Joined: Tue Oct 01, 2019 12:16 am

### Re: Photons and electrons

When given the work function, just think of it as a particular threshold that the energy of the photon must meet or exceed. If that threshold is met, then that implies that there is enough energy to eject the electron.

Arianna Perea 3H
Posts: 50
Joined: Thu Jul 25, 2019 12:17 am

### Re: Photons and electrons

so for every photon that has enough energy, thats the amount of electrons removed?

Rhea Shah 2F
Posts: 97
Joined: Thu Jul 25, 2019 12:17 am

### Re: Photons and electrons

I believe that each photon with enough energy removes one electron, as it was mentioned in lecture that doubling the amount of photons doubles the amount of electrons that are removed. The energy of each photon is the amount necessary to remove the electron plus any excess energy.