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Diffraction gratings Diffraction
gratings are glass plates with many parallel lines etched
into the surface. Any two adjacent lines can be
considered as a two slit setup, and the forumla, |
|
Diffraction gratings Diffraction
gratings are glass plates with many parallel lines etched
into the surface. Any two adjacent lines can be
considered as a two slit setup, and the forumla, |
applies to find the angles where a maximum
occurs in the interference pattern. The difference is
that a much sharper image results. Consider an angle,
just of the maximum, such that the path difference
between the two paths is just one degree off the 360
degrees needed for a maximum. If one then considers the
contribution from a slit 180 etchings away, that
contribution will exactly cancel the first slit, and the
intensity falls all the way to zero. Since the resulting
lines are so sharp, a diffraction grating can be used to
precisely measure wavelengths.