Physics307L F09:People/Dougherty/Photoelectric



Goal
starting the first experiment, we want to determine in summary if it is more likely that light is in form of a wave or in photon form. the photon theory of light says that the energy of light is only determined by frequency and is independent of intensity. however, the wave thoery is only dependent on intensity. the first experiment is investigating this question.

the second experiment wants us to directly measure the constant h and the $$W_0$$, work function, along with the total kinetic energy of the photon. with the total kinetic energy and work function of the photon we can find Planck's constant times the frequency. $$hv=KE_m+W_0$$

How it Works
the photons emitted by the mercury light source enter the h/e apperatus and hit a cathode tube of electrons. the electrons escape the tube with a minimum energy or the work force $$W_0$$. leaving the tube with a max kinetic energy. then by applying a reverse voltage on the energy, we can reverse the energy back to zero recording its stopping potential. this stopping potential is then directly related to the kinetic energy of the electron. plotting voltage vs. frequency we can get h which is planck's constant.

Graphs and Data
http://openwetware.org/wiki/Physics307L:People/Dougherty/Notebook/071001

Our Mean Value
h = 7.13*10^-34    $$W_0$$ = 2.48625*10^-19 J

with mean error

7.13*10^-34 +/- 1.02225242*10^-35

reasons for errors
light filtering in from other sources

bad filters on the apparatus

bad volt meter

most likely the best way to deter from these errors is to have a new volt meter that has been tested to be accurate. and also in pitch black with no other lights or comp lights in the room. these would have the best results