Physics307L:People/Klimov/eDiffraction

Electron Diffraction Summary

Diffraction is a phenomenon that arises from the interference of waves. Until the 20th century, diffraction was believed to be an effect reserved to light (and perhaps water and maybe sound). However, in the early 20th century, an experimental 'accident' led to the discovery that particles, too, could diffract -- that is, particles had some sort of wave nature. Coincidentally, only several years earlier (if i remember correctly), matter waves had been predicted in the doctorate thesis of Louis de Broglie, who claimed that matter must behave like waves in certain limits to preserve the symmetry often observed in nature.

Although the first particles that were observed to diffract were electrons, it has been shown since that essentially anything can diffract, given the correct conditions. Over the course of the century, particle diffraction has become a huge component of various fields of physics and chemistry.

Useful Links:

• Lab Notebook
• Data Analysis

Results

[math]\displaystyle{ Actual Spacing One : .123nm }[/math]

[math]\displaystyle{ Calculated Spacing One (95% confidence interval) : .1237(91)nm }[/math]

[math]\displaystyle{ Error = .55 % }[/math]

[math]\displaystyle{ Actual Spacing Two : .213nm }[/math]

[math]\displaystyle{ Calculated Spacing Two (68% confidence interval): .2157(11)nm }[/math]

[math]\displaystyle{ Error = 1.3% }[/math]

Conclusions

• I am very happy with our results, given that they are so close to the accepted values. The first calculated diameter was within the 95% confidence interval.
• Systematic errors clearly dominated in this lab and I am actually quite surprised that our results turned out as well as they did. I believe that the main source of systematic error was the width of the diffraction maxima, which made it hard to decide on the actual diameter.