## UA Workshop: Question 4 part b

Anna_Mohling_1D
Posts: 40
Joined: Wed Sep 30, 2020 9:56 pm

### UA Workshop: Question 4 part b

4. Zinc metal has a work function of 6.89 x 10-19 J.
a. If UV light with a wavelength of 122 nm is shone on the zinc, what is the kinetic energy of the emitted electrons?

b. What is the longest wavelength of light that will eject an electron from zinc? What is the smallest frequency of light that will eject an electron from zinc? Will wavelengths in the visible light region eject electrons from zinc?

I am stuck on part b. I know the kinetic energy (solved in part a) and I calculated the Ephoton but I am unsure how to finish b. I can't find the answers to this worksheet so if anyone could walk me through b. I'd really appreciate it.

Varsha Ravi 2C
Posts: 35
Joined: Wed Sep 30, 2020 9:48 pm
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### Re: UA Workshop: Question 4 part b

Essentially, since we know we're looking for the longest wavelength possible, we know that there's likely not any excess kinetic energy, so we set that to zero and solve for the energy of a photon setting that equal to the work function. We can solve for the smallest frequency by dividing the work function by Planck's constant, since E = hv, and once we have the frequency, we can solve for the wavelength by dividing c (the speed of light) by the frequency. The wavelength I got (289nm) is in the UV region, and since this is the longest possible wavelength that would eject an electron from zinc, wavelengths in the visible light region would not eject electrons from zinc.