PASCO WA-9316A Complete Microwave Optics System - Manual (Page 41)

013-13906B Teacher’s Guide
41
2. The styrene pellets are very small, compared to the microwave wavelength. Compared to visible wavelengths, the pellets
are enormous. Because of this size difference, optical radiation is scattered by the pellets and microwave radiation is trans-
mitted.
Additional Idea
This apparatus may also be used as a demonstration of how the plane of polarization can be rotated by multiple reflections.
Rotate the transmitter or receiver 90° to each other, so that no signal gets through. Now put the bag of pellets between the two.
If the bag is held straight, there will be a zero meter reading; but if the bag is curved into a spiral, there will be a non-zero read-
ing.
Experiment 11: Brewster’s Angle
Notes on the Procedure
1. through 5.
Answers to Questions
1. Glare off water from a low source is primarily horizontal in polarization, so sunglasses should be designed to block hori-
zontally polarized light.
2. Theoretically, one could do this by finding the point at which there was no transmission of vertically polarized light. We
have not been able to get good results in this experiment, however.
General Notes
1. The index of refraction of the polyethylene is 1.5. (Calculated from the dielectric constant at 10 GHz)
2. One must be careful on this experiment to note that there are actually two effects which are being measured. In addition to
the Brewster’s angle reflection, there is a certain amount of interference between the front- and rear-surface reflections
from the polyethylene. This interference causes extra peaks at 13.8° and 67.2°, and a local minimum at 43.6°. The inter-
ference is notable enough that you may want to demonstrate the interference instead of the Brewster’s angle.
Experiment 12: Bragg Diffraction
Notes on the Procedure
1. The polarization angle of the transmitter and receiver (horizontal or vertical) does not matter.