<text><span class="style10">ave Theory (11 of 11)Diffraction</span><span class="style7">Waves will usually proceed in a straight line through a uniform medium. However, when they pass through a slit with width comparable to their wavelength, they spread out, i.e. they are diffracted. Thus waves are able to bend round corners. For a sound wave of 256 Hz the wavelength is about 1.3 m (4 1/4 ft), comparable with the dimensions of open doors or windows.If a beam of light is shone through a wide single slit onto a screen that is close to the slit, then a bright and clear image of the slit is seen. As the slit is narrowed there comes a point where the image does not continue getting thinner. Instead, a diffraction pattern of light and dark fringes is seen.</span><span class="style26">Huygens' principle</span><span class="style7"> was proposed in 1676 by the Dutch physicist Christiaan Huygens (1629-95) to explain the laws of reflection and refraction. He postulated that light was a wave motion. Each point on a wavefront becomes a new or secondary source. The new wavefront is the surface that touches all the wavefronts from the secondary sources. Diffraction describes the interference effects observed between light derived from a continuous portion of a wavefront, such as that at a narrow slit. The work of the British physician and physicist Thomas Young (1773-1829) and others eventually supported Huygens' theory.AS </span></text>
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<text>ΓÇó QUANTUM THEORY AND RELATIVITYΓÇó ACOUSTICSΓÇó OPTICSΓÇó ELECTROMAGNETISMΓÇó COASTSΓÇó THE OCEANSΓÇó MEDICAL TECHNOLOGYΓÇó RADIO, TELEVISION AND VIDEOΓÇó SEEING THE INVISIBLE</text>
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<text><span class="style10">4. Diffraction of waves</span><span class="style7"> passing through a small gap.</span></text>
