Physics307L:People/Ierides/Electron Diffraction

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Electron Difraction

Please note that Alex Andrego was my lab partner for this lab. You can find her lab summary by following this link.

The purpose of this lab was to study and verify the de Broglie hypothesis that electrons act as waves and particles with the application of the de Broglie equation of [math]\displaystyle{ \lambda=\frac{h}{p}\,\! }[/math]. This was done with the investigation of the electron diffraction through a thin layer of graphite (carbon), which acted as a diffraction grating.

Prof. Gold's Lab Manual served as a loose guideline for our lab procedure and our "Brief Description of Electron Diffraction" above as well as the source of the accepted values of the separation of the carbon atoms corresponding to the inner and outer ring diameters
Darrell Bonn's Electron Diffraction Lab served as a greatly needed set-up guide for our circuit

SJK Incomplete Feedback Notice

Incomplete Feedback Notice
My feedback is incomplete on this page for two reasons. First, the value of the feedback to the students is low, given that the course is over. Second, I'm running out of time to finish grading!

Data and Analysis

SJK 18:42, 15 December 2009 (EST)

18:42, 15 December 2009 (EST)
Better than just calculating percent error would be comparing the distance from the accepted value relative to your range of uncertainty.
The calculated [math]\displaystyle{ d\,\! }[/math] for the inner diameter,
[math]\displaystyle{ d\simeq0.177 nm\,\! }[/math]
With a range of:
[math]\displaystyle{ 0.154 nm \leq d \leq 0.206 nm\,\! }[/math]
And percentage error:
[math]\displaystyle{ \% error=\frac{d_{inner}-d_{measured, average}}{d_{inner}}\,\! }[/math]
[math]\displaystyle{ \% error=\frac{(0.213 nm-0.177 nm)}{0.213 nm}\,\! }[/math]
[math]\displaystyle{ \simeq16.9%\,\! }[/math]
The calculated [math]\displaystyle{ d\,\! }[/math] for the outer diameter,
[math]\displaystyle{ d\simeq0.0893 nm\,\! }[/math]
With a range of:
[math]\displaystyle{ 0.0821 nm \leq d \leq 0.0979 nm\,\! }[/math]
And percentage error:
[math]\displaystyle{ \% error=\frac{d_{outer}-d_{measured, average}}{d_{outer}}\,\! }[/math]
[math]\displaystyle{ \% error=\frac{(0.123 nm-0.0893 nm)}{0.123 nm}\,\! }[/math]
[math]\displaystyle{ \simeq27.1%\,\! }[/math]


Our results had a substantial amount of error involved. This could be due to some oversight of the uncertainty and systematic error mentioned in the notebook. If we had a chance to retake data, I would certainly have placed the calipers with more precision on the bulb to measure the correct diameter of each ring at each corresponding voltage. Overall I believe we had taken a substantial amount of data and had worked very hard on this lab, although our errors would prove that the data taken might not have been up to par.