Go Back to Unit IV Menu 1. The spherical waves from a nearby lamp have noticeable curvature. Diffraction is most pronounced for long-wavelength waves. The wavelength of sound waves is relatively long, and for light waves extremely short. Hence it is the diffraction of sound that is most evident in our everyday environment.
Radio waves have much longer wavelengths than light and therefore diffract more.
The alternation of sound from loud to soft is evidence of interference. If the listener walks along the perpendicular bisector of the line connecting the speakers, the listener will, at all points, be equidistant from both speakers. Tones from both speakers will be in phase all along this path. A bit of thought will show you there are other paths of non-cancellation as well. Both interference fringes of light and the varying intensities of sound are the result of the superposition of waves that interfere constructively and destructively.