# Physics307L:People/Phillips/Photoelectric

(Difference between revisions)
 Revision as of 20:37, 6 December 2008 (view source) (→Data & Results)← Previous diff Revision as of 20:47, 6 December 2008 (view source) (→Data & Results)Next diff → Line 33: Line 33: $\% error^{2}_{second order} = 14.8\%$ $\% error^{2}_{second order} = 14.8\%$ + + All of the above numbers enumerate our results for Planck's constant, but we also measure what the work function must be for the cathode that the light is incident upon. We obtained four total values for this as well, from the four runs mentioned above, but there is no accepted value to compare it with. + + $W^{1}_{0} = (2.43 \pm .06) \times 10^{-19}~\mathrm{J} = (1.52 \pm .04)~\mathrm{eV}$ + + $W^{2}_{0} = (2.47 \pm .04) \times 10^{-19}~\mathrm{J} = (1.54 \pm .03)~\mathrm{eV}$ + + $W^{3}_{0} = (1.47 \pm .35) \times 10^{-19}~\mathrm{J} = (0.922 \pm .22)~\mathrm{eV}$ + + $W^{4}_{0} = (1.41 \pm .35) \times 10^{-19}~\mathrm{J} = (0.884 \pm .22)~\mathrm{eV}$

## Revision as of 20:47, 6 December 2008

### Photoelectric Effect (Planck's Constant) Summary

#### Data & Results

The notebook entry for this lab is located here. We generated two Excel files for this lab as well: Planck.xlsx and First Order.xlsx.

In this lab, we showed by experiment that the energy stored in light is proportional to it's frequency (not amplitude) and determined what this constant of proportionality is, as well as another constant that shows up from photoelectric effect theory.

We measured two different things in this lab related to the photoelectric effect, but only one of these has an accepted value - Planck's Constant. This value is

$h_{acc} = 6.626\,068\,96(33) \times 10^{-34}~\mathrm{J}\cdot\mathrm{s} = 4.135\,667\,33(10) \times 10^{-15}~\mathrm{eV}\cdot\mathrm{s}$

We came up with many different value for Planck's constant. We obtained two from the first order maxima from the light source, each being a separate run through the colors:

$h^{1}_{first order} = (6.911 \pm .087) \times 10^{-34}~\mathrm{J}\cdot\mathrm{s} = (4.319 \pm .054) \times 10^{-15}~\mathrm{eV}\cdot\mathrm{s}$

$h^{2}_{first order} = (6.978 \pm .059) \times 10^{-34}~\mathrm{J}\cdot\mathrm{s} = (4.361 \pm .037) \times 10^{-15}~\mathrm{eV}\cdot\mathrm{s}$

each with percent errors from the accepted value of

$\% error^{1}_{first order} = 4.30\%$

$\% error^{2}_{first order} = 5.32\%$

Along with these first order values, we also ran through the experiment using only the second order maxima, obtaining different values for Planck's constant:

$h^{1}_{second order} = (5.74 \pm .51)\times 10^{-34}~\mathrm{J}\cdot\mathrm{s} = (3.59 \pm .32) \times 10^{-15}~\mathrm{eV}\cdot\mathrm{s}$

$h^{2}_{second order} = (5.65 \pm .52)\times 10^{-34}~\mathrm{J}\cdot\mathrm{s} = (3.53 \pm .32) \times 10^{-15}~\mathrm{eV}\cdot\mathrm{s}$

again with respective percent errors from the accepted value

$\% error^{1}_{second order} = 13.4\%$

$\% error^{2}_{second order} = 14.8\%$

All of the above numbers enumerate our results for Planck's constant, but we also measure what the work function must be for the cathode that the light is incident upon. We obtained four total values for this as well, from the four runs mentioned above, but there is no accepted value to compare it with.

$W^{1}_{0} = (2.43 \pm .06) \times 10^{-19}~\mathrm{J} = (1.52 \pm .04)~\mathrm{eV}$

$W^{2}_{0} = (2.47 \pm .04) \times 10^{-19}~\mathrm{J} = (1.54 \pm .03)~\mathrm{eV}$

$W^{3}_{0} = (1.47 \pm .35) \times 10^{-19}~\mathrm{J} = (0.922 \pm .22)~\mathrm{eV}$

$W^{4}_{0} = (1.41 \pm .35) \times 10^{-19}~\mathrm{J} = (0.884 \pm .22)~\mathrm{eV}$