## Photoelectric Effect Post-Assessment #22 & 23

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Cobie_Allen_1H
Posts: 24
Joined: Wed Sep 21, 2016 2:56 pm

### Photoelectric Effect Post-Assessment #22 & 23

#22 states that "Molybdenum metal must absorb radiation with a minimum frequency of 1.09 x 1015 s-1 before it can emit an electron from its surface. Answer the following two questions."

I understand how to answer 22 ("What is the minimum energy needed to produce this effect?"), but I am confused on how to get the answer for #23. Can someone please explain how to get the answer?

The question states: "If molybdenum is irradiated with 194 nm light, what is the maximum possible kinetic energy of the emitted electrons?"

Jenna_Hakel_2A
Posts: 34
Joined: Fri Jul 15, 2016 3:00 am

### Re: Photoelectric Effect Post-Assessment #22 & 23

For 23, I used the equation E=(hc)/wavelength to find the energy of the light with the wavelength of 194 nm. I then subtracted the number that I calculated in #22 (since that is where we calculated the threshold energy for the metal) according to the equation E(light)=threshold energy + KE(electron). Doing this should leave you with the kinetic energy of the electrons emitted! So, (energy of light calculated from wavelength)-(threshold energy calculated in #22)=(kinetic energy of electrons). Hope that helped!

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