Page 1 of 1

### Equations

Posted: Fri Oct 12, 2018 11:28 am
I know that E=hv is for the energy of the incoming photon, but can Ek=1/2mv^2 also be used to describe the kinetic energy of the photon, or is it only used for the kinetic energy of electrons?

### Re: Equations

Posted: Fri Oct 12, 2018 12:04 pm
I think this equation only applies to the kinetic energy of the electrons that are emitted. I don't think this equation would work with photons because photons do not have mass. The energy of a photon comes from its frequency, E=hv, which is only kinetic energy because light is not stationary.

### Re: Equations

Posted: Fri Oct 12, 2018 12:10 pm
The energy of a photon is determined by the equation hv. This energy is absorbed by the electron that is either ejected (if the energy of the photon is greater than work function) or remains.

A key thing to understand that may help answer your question is that the equation (1/2)mev2 = hv- work function. So, therefore, the (1/2)mev2 does not equal kinetic energy of a photon.

**page 13 in the textbook (version 6) may help further

### Re: Equations

Posted: Sat Oct 13, 2018 11:09 am
Do the same parameters for when to use this equation apply to the wavelength formula or any others that we're using in this section?