Apologies, but I have another photoelectron question. In this one I get a result that seems reasonable, however it does not show up on my list of work functions that I have available to choose from. The problem is:(adsbygoogle = window.adsbygoogle || []).push({});

A photoelectric-effect experiment finds a stopping potential of 1.93V when light of 200nm is used to illuminate the cathode. What is the cathode made of?

I initially thought this would be an easy problem as Vstop = (hf - Eo) / e

I have all the values except Eo which is what I am trying to solve for.

Vstop = 1.93 V

h = 4.14x10^-15 eV

f = 3x10^8/200x10^-9 = 1.5x10^15

e = 1.6x10^-19

So, I plug all of the values into the equation and solve for Eo

1.93 = ((4.14x10^-15)(1.5x10^15)-Eo)/1.6x10^-19

The resulting value of Eo was 6.21

This seems valid, except the list I have to choose from is:

Potassium: 2.3

Sodium: 2.75

Aluminum: 4.28

Tungsten: 4.55

Copper: 4.65

Iron: 4.7

Gold: 5.1

Likely I am having the same problem as my previous question and not seeing a simple unit difference. Anyhow, I do appreciate your help.

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# Homework Help: Finding the work function using stop potential

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