# Photoelectric Effect and ozone layer

1. Oct 27, 2007

### fireandwater

Hi. I hope someone can help. Here is the problem:

[Pennies are made of zinc coated with copper. Copper has a work function of 4.7eV. The ozone layer blocks nearly all solar radiation with wavelength shorter than 320nm, but a very small amount of 200nm light still manages to reach the Earth's surface. Can direct sunlight produce photoelectrons from a penny?]

I converted the 4.7eV into joules: 4.7eV * 1.602e-19J = 7.529e-19J
I found the minimum kinetic energy needed to for the electrons to escape from the copper:
KE = e * V_o => 1.602e-19 * 7.529e-19 = 1.206e-37J

I'm thinking that I need to use the 200nm to find out whether the kinetic energy I calculated will be produced by the sunlight, but I don't see how to do that.

2. Oct 27, 2007

### Chi Meson

Your reasoning is incorrect. KE = E - W (E is energy per photon, W is work function, KE is max kinetic energy of photoelectron).

Stay in eV, it's easier. Use 4.14 x 10^-15 eVs as h.

Energy per photon is hf =hc/wavelength.

How much energy in a 200 nm photon?

Last edited: Oct 27, 2007
3. Oct 27, 2007

Thank you!