Quick question on kinetic energy  [ENDORSED]

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melissasandoval2O
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Joined: Fri Jul 15, 2016 3:00 am

Quick question on kinetic energy

Postby melissasandoval2O » Sat Oct 01, 2016 9:09 pm

So I was looking at the lecture notes and I understand E(photon) = threshold energy + E(excess). So if the energy required to remove the electron is equal to the energy of the photon, where does that leave the kinetic energy, is it equal to zero?

Raj Susarla 3I
Posts: 28
Joined: Wed Sep 21, 2016 2:56 pm

Re: Quick question on kinetic energy  [ENDORSED]

Postby Raj Susarla 3I » Sat Oct 01, 2016 10:34 pm

Yes, this essentially means that the kinetic energy of the electron is equal to zero. For our uses and purposes, you will usually see questions which will specify "an electron with zero kinetic energy" so you know this is the case. Conceptually, however, it is tricky to understand what this would mean. Dr. Lavelle described it like this: when the photon has the same energy as the threshold (aka just enough to remove the electron), the electron will be emitted. The metal will then be left with a slight positive charge, and the electron is likely to be electrostatically attracted back, as it hasn't been ejected with any velocity. I doubt we will need that much depth, but thought it might be helpful for you!


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