We developed two experiments for demonstrating the interference of waves using commonly available tools and materials. The interference of sound can be observed in an outdoor setting using a smartphone with a free application, a USB power pack, and a pair of computer speakers. The coherent sound waves from the two separated speakers create easily identifiable points of destructive interference. The interference of light can be demonstrated by cutting lines in electric tape adhered to a microscope slide and using a coherent light source such as a laser pointer. The single- and double-slit interference patterns can be observed on a screen placed some distance from the source.
For interference of sound, we downloaded Audio Function Generator1 for an Apple iPhone 6 using iOS and Waveform Generator Demo2 for a Samsung Galaxy S4 using Android OS. Both of these applications generated sinusoidal waveforms over a wide range of audio...