The thunder from a close bolt of lightning will be experienced as a sharp crack, indicating the presence of a lot of high frequency sound. Another common example of diffraction is the contrast in sound from a close lightning strike and a distant one. The fact that diffraction is more pronounced with longer wavelengths implies that you can hear low frequencies around obstacles better than high frequencies, as illustrated by the example of a marching band on the street. Diffraction in such cases helps the sound to "bend around" the obstacles. The fact that you can hear sounds around corners and around barriers involves both diffraction and reflection of sound. Important parts of our experience with sound involve diffraction. The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Adam Augustyn.Diffraction of Sound Diffraction of Soundĭiffraction: the bending of waves around small* obstaclesand the spreading out of waves beyond small* openings.* small compared to the wavelength When a stream of fast particles impinges on the atoms of a crystal, their paths are bent into a regular pattern, which can be recorded by directing the diffracted beam onto a photographic film. When a beam of light falls on the edge of an object, it will not continue in a straight line but will be slightly bent by the contact, causing a blur at the edge of the shadow of the object the amount of bending will be proportional to the wavelength. When sound of various wavelengths or frequencies is emitted from a loudspeaker, the loudspeaker itself acts as an obstacle and casts a shadow to its rear so that only the longer bass notes are diffracted there. The phenomenon is the result of interference (i.e., when waves are superimposed, they may reinforce or cancel each other out) and is most pronounced when the wavelength of the radiation is comparable to the linear dimensions of the obstacle. One consequence of diffraction is that sharp shadows are not produced. Diffraction takes place with sound with electromagnetic radiation, such as light, X-rays, and gamma rays and with very small moving particles such as atoms, neutrons, and electrons, which show wavelike properties. See all videos for this articleĭiffraction, the spreading of waves around obstacles. Learn about diffraction of sound, electromagnetic radiation, and small moving particles.
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