PASCO WA-9316A Complete Microwave Optics System - Manual (Page 38)

Experiment Guide Teacher’s Guide
38
2. Single-slit diffraction may also be attempted on this apparatus, though we don’t recommend it. The distances are too short,
relative to the wavelength; so the analysis requires the Fresnel/Kirchoff approach instead of the Fraunhoffer approxima-
tion. Even with the Fresnel approach, the “fringes” are too small to be seen adequately.
• Basically, it doesn’t work well at all.
Experiment 7: Lloyd’s Mirror
Notes on the Procedure
Average: 27.59 mm
Standard deviation: 1.37
An alternate method is to graph path length versus fringe number and take
the slope of the graph. This slope will be the wavelength.
Answer to the Question
• It simplifies the calculations.
Fringe h (mm) Path length (mm) Wavelength (mm)
1 85 720
2 138 752 32.10
3 171 779 26.63
4 200 806 27.15
5 227 834 28.11
6 251 861 27.06
7 276 890 28.83
8 298 919 29.13
9 317 944 25.08
10 338 973 28.69