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### Threshold Energy

Posted: Sun Apr 15, 2018 12:51 am
How do we figure out what the threshold energy is? Or will it be given when needed?

### Re: Threshold Energy  [ENDORSED]

Posted: Sun Apr 15, 2018 11:07 am
Threshold energy is the energy required to eject an electron. You will not always be given the threshold energy. There is an equation (KE of ejected electron = E of photon - threshold energy). If any of the other values are given, you may have to solve for the threshold energy.

### Re: Threshold Energy

Posted: Sun Apr 15, 2018 12:36 pm
If you are given the energy of the photon and the excess energy, you can solve for the threshold energy by adding them together.

### Re: Threshold Energy

Posted: Sun Apr 15, 2018 5:29 pm
It really just depends on what is given to you in the problem. Some problems will give you the threshold energy. Some will not and in these types of problems, you will have to solve them. Meaning using the equation Lavelle gave to us in class, Energy of the photon- threshold energy= kinetic energy of the ejected electron=excess energy and applying basic arithmetic.