Physics307L:People/Klimov/Photoelectric

Planks Constant

The photoelectric effect is an important experiment in the history of physics because it clearly displays the quantum theory of light. The photoelectric effect describes the emission of photoelectrons due to the absorption of light quanta, photons. According to Einstein's theory, each photon carries a certain amount of energy that is proportional to the frequency of light (not intensity, as in classical theory). The proportionality constant is the famous Plank constant. In this lab, we set out to find the value of this constant by measuring the stopping potential of a circuit, whose current is 'generated' by photoelectrons. In addition to measuring the Plank constant, this method also allows one to measure the work function of the metal.

Data

[math]\displaystyle{ h_{meas} = 7.26(14)\cdot 10^{-34} J \cdot s }[/math]

[math]\displaystyle{ h_{act} = 6.626\cdot 10^{-34} J \cdot s }[/math]

[math]\displaystyle{ W_{meas} =1.635(48) V^{} }[/math]

[math]\displaystyle{ W_{act} = 1.36 V^{} }[/math]

Conclusions

• Although I am happy with our results, I am not particularly happy with the lab set up. I believe that we got good data, given that it fit perfectly to a straight line. I believe there is some source of systematic error that prevailed in this lab.