# Photoelectric effect: Experimental Physics

Suppose you are doing an experiment to determine the work function of a metal.  You get $KE_1$, $\nu_1$ and $KE_2$, $\nu_2$.   We know that $KE = h\nu - W$ but when you solve the simultaneous equations, we have a $h$ slightly different from the textbook value.

Question: In such a situation should you

1. Use the textbook $h$ then average {$W_1,W_2$}; or

2. Simply solve the simultaneous equations for $W$

I believe that the values obtained will be different.

Thank you.

Added: Assume you don't get to do more repeats etc.

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Look up work funktion values for metals in eg CRC Handbook. You will see those are given for just one digit after the point. This shows the accuracy of the experiments. Which h to choose then is secondary. – Georg Oct 14 '11 at 16:45

You should definitely use the textbook value of $h$. In any experiment there are always (hopefully) small errors in measurements so the fact that you get two different values for the work function $W$ from two different experiments is to be expected. Average those $W$s and consider their difference to be a rough estimate of the potential error.