Purpose:  To become familiar with the microwave optics system by measuring the intensity of microwaves as a function of distance and angle from the transmitter, and observing the polarization and reflection properties of the microwaves.

Discussion: The microwave optics apparatus is a convenient way to study electromagnetic wave phenomena. The relatively long wavelength of approximately 3 cm creates standing wave patterns and interference phenomena on a larger scale than visible light. You will be doing a series of experiments based on the Pasco Microwave optics manual which accompanies the equipment. Note that the receiver has been modified to connect to an external power supply.

Procedure:

1. Set up the system as described in steps 1-5 on p. 8 of the manual and make a data table similar to Table 1.1. Record the meter reading M every 5.0 cm.

2. Make a graph of M vs. r. Comment on the shape of the graph and the contents of the third and fourth columns of your table (Is one of these columns a constant?).

3. Perform step 6 on p. 8 and record your qualitative observations regarding the reflection of microwaves from nearby objects.

4. Perform step 7 on p. 9 and record your qualitative observations regarding the polarization of the microwaves.

5. Perform step 8 on p. 9. Record the meter reading M every 5°.

6. Make a graph of M vs. q. Comment on the shape of the graph.

7. Perform the reflection measurements as described in steps 1-5 on p. 10. Record your values of qi (the angle of incidence) and qr (the angle of reflection) in a table similar to Table 2.1. You will have to do some careful subtracting in order to determine qi and qr . Record qr as you increase qi in increments of 5°. Notice that you cannot make the angle of incidence very small. Be particularly careful with extraneous reflections from nearby objects as well as microwaves which travel directly from the transmitter to the receiver without being reflected from the metal reflector.

8. Make a graph of qr vs. qi. Do the microwaves obey the law of specular reflection?

9. Metal is a good reflector of microwaves. Investigate the reflective properties of other materials. How well do they reflect? Does some of the energy pass through the material? Is some of the energy absorbed by the material? Compare the reflective properties of conductive and non-conductive materials.