Manhattan Center for Science and Mathematics
Summer 2001

Wave Nature and Wavelengths of Microwaves

Aim/Problem:  1. Can we demonstrate the wave nature of microwaves?
2. Can we determine the wavelength of a microwave?

Objectives:    The student will be able to
1. Recall the wave phenomena - reflection, refraction,  diffraction, interference, and polarization.
2. Agree upon an appropriate procedure for testing whether microwaves are waves.
3. Extend that procedure to determine the wavelength of the microwaves. (frequency as well)
4. Compare the measured frequency to published microwave frequencies (such as in a textbook or NYS Regents tables).

Materials:       Microwave Diffraction Kit (which should include:)
- Microwave Source
- Microwave Detector
- Metal slits of varying width
- Polarizers
- Reflecting surfaces
- Meter Sticks
- New York State Physics Regents Reference Tables (or equivalent)

Plan:      1.  Students will first be briefed in the safe use of the equipment.
2. Students will meet (briefly) to establish procedures for solving the problem. Note that steps 1 and 2 could occur in class the day before                     the lab period. (Standards S5a, S8a)
3. The teacher will monitor student progress in solving the  problem. In the event that a group becomes stuck, the teacher can ask a                       series of leading questions to encourage groups toward a sensible procedure. In the approximate order that they may be relevant some                      such questions are:

- If it is a wave, what must it be able to demonstrate?
- Have you measured a slit to detector distance? (L)
- Have you moved the detector to different locations?
- Have you measured the distance between the slits? (d)
- How will you determine the distance from the central order to the first order? (x or sin0 = x/L)
- How will you determine the wavelength of the microwave? (use Young's Double Slit wavelength = xd/L = dsin0)
- How might you check that wavelength? (Try a slit with different spacing)
- Is it a longitudinal or transverse wave? ( use the polarizing filter to determine)
- How will you find the frequency? (c = f * wavelength)
- Is your frequency comparable to those on the reference tables? (Standards S1f, S5b, S5e)

4. As a post lab exercise, students can be encouraged to share results, look for novel approaches to data collection or presentation, average         results, and suggest improvements to the lab. (Standard S5f)
5. Students complete report following the conventions outlined on the handout. The report should detail the chosen method (procedure),         present the data, and describe a the solution to the problem. The discussion section challenges students to infer the importance of this          lab to astronomy. (Standards S6b, S6c)
6. A future lesson will review the achievements of non-visible light astronomy.

Regents Physics Laboratory - Microwave Diffraction

Problem: 1. Can we demonstrate the wave nature of microwaves?
2. Can we determine the frequency of a microwave?

Materials:    Microwave Source                                   Meter Sticks
Microwave Detector                                NYS Physics Regents Tables
Metal Slits                                                Polarizers