Standing waves (micro or sound) in an adjustable cavity.

Standing waves (micro or sound) in an adjustable cavity. This is a comparison between standing microwaves and standing sound waves, using the same cavity. In setup 'A', a 3 cm. wavelength microwave transmitter sends 10 GHz microwaves to a 'resonant cavity' brass tube that has a moveable plunger. A 3 cm. loop antenna 'folded dipole', with a detector diode in the base of the handle, is placed near the mouth of the tube. This antenna detects the signal amplitude of the standing wave which can be displayed on the milliameter, or can be heard as a tone emitted from the speaker. As the plunger is moved in and out of the tube, the antenna detects maximums and minimums of the standing microwave. In setup 'B', most of the equipment is removed. Only the 2900 Hz Sonalert sound source is held by hand in front of the brass tube. The plunger is moved in and out of the tube, and nodes and antinodes can be clearly heard. The wavelength of the Sonalert is about 12 cm. (Note: A newer version of transmitter can be substituted. See file cabinet folder for details.)