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Experiment 7: lloyd’s mirror – PASCO WA-9316A Complete Microwave Optics System User Manual

Page 38

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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