Diffraction
Diffraction, property of wave motion, in which waves spread and bend as they pass through small openings or around barriers. Diffraction is more pronounced when the opening, or aperture, or the barrier is similar in size to or smaller than the wavelength of the incoming wave. Diffraction is a property of the motion of all waves. For example, if a radio is turned on in one room, the sound from the radio can be heard in an adjacent room even from around a doorway. Similarly, whenever water waves pass an object on the surface of the water, such as a jetty or boat dock, waves that pass the object's edge spread out into the region behind the object and directly blocked by it. To understand this effect, Dutch physicist Christiaan Huygens proposed that each point of a wave on a flat wave front, or crest, acts like a source of secondary, spherical wavelets, or smaller waves. Before reaching a barrier, these secondary wavelets add to the original wave front. When the wave front approaches