![]() The third figure, for example, shows a comparison of a single-slit pattern with a pattern formed by five slits, both sets of slits having the same spacing, d, between the center of one slit and the next. When the diffracting object is repeated, the effect is to narrow each maximum, concentrating its energy within a narrower range of angles.The diffraction angles are invariant under scaling that is, they depend only on the ratio of the wavelength to a dimension, d, of the diffracting object.(More precisely, this is true of the sines of the angles.) When the dimensions of the diffracting object are reduced, the angular spacing of the diffraction pattern is increased in inverse proportion.Several qualitative observations can be made: Historically, the first proof that light was a wave phenomenon came from the double-slit experiment of Thomas Young. The destructive-interference locations are the minima. The constructive-interference locations are called maxima, because they have maximum brightness. The second figure shows the result of this process with light waves of a single wavelength originating from a laser. However, when a trough and a crest overlap, they cancel out the interference is destructive. Constructive interference also occurs where a trough overlaps another trough. Where a crest overlaps with a crest, a double-height crest will be formed this is constructive interference. After passing through the slits, two overlapping patterns of semicircular ripples are formed, as shown in the first figure. Suppose, for the sake of visualization, that these are water waves. The most conceptually simple example of diffraction is double-slit diffraction in which both slits have relatively narrow widths compared to the wavelength of the wave. Double-slit diffraction of red light from a laser.
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