Diffraction effects with a double slit
Note that diffraction can be observed in a doubleslit interference pattern. Essentially,
this is because each slit emits a diffraction pattern, and the diffraction patterns
interfere with each other. The shape of the diffraction pattern is determined by the
width (W) of the slits, while the shape of the interference pattern is determined by d,
the distance between the slits. If W is much larger than d, the pattern will be
dominated by interference effects; if W and d are about the same size the two effects
will contribute equally to the fringe pattern. Generally what you see is a fringe pattern
that has missing interference fringes; these fall at places where dark fringes occur in
the diffraction pattern.
Diffraction gratings
We've talked about what happens when light encounters a single slit (diffraction) and
what happens when light hits a double slit (interference); what happens when light
encounters an entire array of identical, equallyspaced slits? Such an array is known as
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 Fall '10
 DavidJudd
 Physics, Diffraction, Wavelength, Diffraction grating

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