Calculations and data analysis were carried out using the programs MatLab and Maple.
The work done in Maple involves the conversion of the ring heights from those projected on the curved surface of the electron diffraction tube to ones that would be seen on a flat screen tangent to the center of the tube.
The work done in MatLab consists of all numerical calculations to find the spacing between molecules in the graphite crystal lattice, along with finding the error relative to known values of the spacing.
The calculations done in Maple can be accessed at File:Electron diffraction.mw. NOTE: the file is in the format of a maple worksheet and cannot be properly opened outside of Maple.
The calculations done in MatLab can be accessed at File:ElectronDiffraction.doc.SJK 02:09, 19 October 2008 (EDT)02:09, 19 October 2008 (EDT) I did look over your word document, and it is pretty easy to follow. However Can you please for the following labs upload figures directly here as images, to show things like linear fit. It would be best if you don't rely on word at all, but if you do still want to, at least make looking at the word document more of a supporting role. That will help out me and other students reading your work.
As far as the word document goes, I would much rather have seen the data with the linear fit shown (rather than the jagged line connecting the points
From my calculations, the spacing in the crystal lattice of graphite calculates as [math]\displaystyle{ d=.109nm, .203nm }[/math], whereas the accepted values are [math]\displaystyle{ d=.123nm, .213nm }[/math]
That gave a percent error of 11.7% on the .123nm distance and 4.9% on the .213nm distance.
Using the largest value within the calculated error of [math]\displaystyle{ d=.003nm, .006nm }[/math] the percent error calculated to be 8.9% and 2.0%.
A graph of D (the extrapolated ring diameter) against the square-root of the anode Voltage, showed an approximate linear relationship, which proves that De Broglie's hypothesis is correct as the linear relationship is seen between the momentum of the particle and its wavelength due to the uncertainty in it's position.
Therefore, my final values for the lattice spacing are [math]\displaystyle{ d=.109(3)nm and .213(6)nm }[/math]
SJK 02:25, 19 October 2008 (EDT)02:25, 19 October 2008 (EDT) Another consequence of having some stuff buried in the word document is that it's tough to find out where you get your error values. I think I determined it is from your estimate of the uncertainty in length of the tube. Whereas using standard error of your means gives you much lower uncertainty value?SJK 02:32, 19 October 2008 (EDT)02:32, 19 October 2008 (EDT) You mention somewhere that your data looked reasonably linear when plotted versus V^2. You should have done a linear fit in matlab, and then looked at the uncertainty in this fit slope as another way of getting uncertainty on your final value!
Electron Diffraction
Main project page
Previous entry Next entry
