Analog of Optical Elements or Sound Waves in Air

摘要

Optical elements manipulate light waves. They may be used to focus the light or to change the phase, the polarization, the direction,or the intensity of light. Many of these functions areoften demonstrated with microwaves, since the devicesnormally available in teaching laboratories producewavelengths in the centimeter range and are thereforemore tangible. The same can be said for sound wavesfor frequencies in the kHz range. This property is theclue for producing elements such as half-wave plates,zone plates, and lenses for sound waves, based on tech-niques that have been developed for microwaves. Thisis the subject of the present article. Readers might wishto build some of these devices, which would then helpto impress on students the unity of wave phenomena.