Diffraction

Figure 11.2: Waves can even bend around corners, due to diffraction. A top-down view of a room is shown. At each of the three interior corners, the propagating wavefront expands around it.

Wavefronts can also bend around corners, which is called diffraction; see Figure 11.2. This would enable someone to hear a sound that is around the corner of a building, without relying on any reflection or transmission. More diffraction occurs for longer wavelengths; thus, a lower-pitched sound bends around corners more easily. This also explains why we are more concerned about acoustic diffraction in a room than light diffraction, although the latter is often important for lenses (recall the Fresnel lens drawback of Section 7.3).