Number of photons

[Jessica Hu 3L]

If you're given a wavelength and energy required to absorb the radiation, how can you tell how many photons you need?

[Sophia Hu 1A]

Typically the energy of a photon has the units Joules per photon. So if you use the wavelength to find energy of the photon with the equations E=hv and c=v*lambda then this should give you the J/photon. Then you are usually given another value that states a certain amount of Joules were released by the light. You would then use this given energy and divide it by the energy of the photon. Doing this cancels the units of Joules out and gives the answer in photons, so you know this will give you the number of photons.

Hope this helps! If there is a specific question you are confused about I can try to help you with it. It might be easier than an explanation.

[Melody Wu 2L]

The energy required to absorb radiation is the work function, which is given in units of J/mol. There are 6.022E23 photons in one mole (Avogadro's #) so all you need to do it divide by Avogadro's # to find J/photon.

[Jessica Hu 3L]

okay thank you!