User:Michael R Phillips/Notebook/Physics 307L/2008/11/26
Planck's Constant Lab | <html><img src="/images/9/94/Report.png" border="0" /></html> Main project page <html><img src="/images/c/c3/Resultset_previous.png" border="0" /></html>Previous entry<html> </html> |
Planck's Constant (Photoelectric Effect)Introduction & SafetyFor this lab, we will be measuring a value for Planck's constant (h) by relating it to photoelectric effects caused by a Mercury lamp's light incident upon a cathode. There a few safety concerns that we will need to be careful about. These are high voltage, hot Mercury tube, and risk of breaking the tube or lens/grating. Most of these hazards have already been dealt with in previous labs (see Balmer Series) so we were already prepared for them. The only other important thing to note as far as safety is, as Aram pointed out, that we do not want to allow too strong of an intensity of light into our h/e apparatus because it could be damaging. To account for this, we will make sure to attach a filter which will simply decrease the intensity of light entering the apparatus. Setup & EquipmentEquipment
ProcedureBefore really getting started, we had to make sure our battery in the h/e apparatus still had enough voltage, so we connected the multimeter in parallel with the "Battery Test" connectors on the apparatus. We know, from the manual and from speaking with Aram, that the apparatus has two 9-volt batteries inside, giving a maximum potential of 18V if the batteries were new. The apparatus shows the minimum values, indicating ±6V which gives us a minimum of 12V that could be read through our multimeter. We actually measured our maximum potential to be [math]\displaystyle{ V_{max}=(16.091 ± .001)V }[/math] which is between the maximum possible (i.e. new batteries) and minimum possible (i.e. old batteries, not enough to stop photon energy) potentials.
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