Purpose:Demonstrate how sound waves can be focused by concave reflectors.
Description:Set the oscillator at about 3000 Hz for best results. Install speaker at the focus of one reflector and microphone at focus of second reflector; the oscilloscope views the microphone output. With the positions of all elements optimized the sound from the speaker reflects off its mirror to create a beam of sound, which is focused by the second mirror onto the microphone. All elements may be adjusted to verify the existence of foci.
When discussing wave phenomena, this can be usefully compared to optical focusing demonstrations in section L.