Planck’s Constant
Data Analysis
- Show a plot of your photocurrent(i.e. voltage indicating the photocurrent) Vs. retarding voltage data for one wavelength of light with the iris mostly open and with the iris mostly closed. How does the increased light intensity change the signal? Are there aspects of the signal that remain the same?
- For one iris setting, by eye, estimate the retarding voltage at which the current from the cathode begins to grow exponentially for each wavelength of light that you used. Summarize these results in a plot of retarding potential-at-onset as a function of frequency.
- Fit your data from the previous step using a straight line, the slope of which should be
. Determine 
using the CODATA value for the elementary charge: 1.602176634×10−19 C. - Repeat steps 3 and 4 for the other iris setting.
- Compare your values to eachother and to the CODATA value for h