Procedure

Microwave Diffraction

4.1 Reflection

You’ll start off with some relatively simple reflection measurements to get used to the apparatus.

Arrange the Transmitter and Receiver in a straight line, with each component about 30 cm away from the center. Make sure the two components are oriented to the same polarization (at the same angle). Set the reading on Receiver to near full scale.
Place the reflector between the two components and check that the Receiver is measuring zero (or very near zero).
Rotate the transmitter, receiver, and plate so that the angle of incidence and reflection are 20 $^{\circ}$ .
Rotate the Receiver and find the angle with the highest signal. Record your value.
Repeat measurements every 10 $^\circ$ up to 80 $^\circ$ .
Plot your data. Is there a relationship between the angle of incidence and angle of reflection? Does the relationship break down at any point? Is it the relationship you expected?

Arrange the Transmitter and Receiver back to a straight line, with each component between 10 and 20 cm away from the center.
Add the double-slit panels to the magnetic strip. The slits need to be about 1.5 cm wide, with the center of the slit pattern inline with the Transmitter.
Adjust the Receiver so that you measure the maximum signal on the lowest gain setting possible.
Rotate the Receiver from 0 $^\circ$ to 85 $^\circ$ in increments of 2 $^\circ$ and record the Receiver measurement. You should be able to see the constructive and destructive interference. Be sure to plot your data as you go. There’s nothing worse than spending all that time making a table of useless data.

Replace the reflector with the lattice cube. Arrange the Transmitter and Receiver back to a straight line with the cube perpendicular to the wave.
Adjust the Receiver so that the signal is at about half of the dynamic range of the scale.
Rotate the lattice by 1 $^\circ$ and the Receiver by 2 $^\circ$ (keeping with Bragg’s law) and record the Receiver value. Hopefully you won’t have to change the scale of the Receiver, but if you do, then make a clear note of doing that and account for it when you plot your data. Or consider going back and restarting your data collection of you haven’t sunk too much time into it, yet.
Use your data, the wavelength of the microwaves, and Bragg’s law to determine the spacing between the (100) planes of the lattice. Measure the distance directly and compare.
Repeat this measurement for the (110) plane and, if you have time, the (210) plane.