a broad beam of light of wavelength 620 nm is sent directly downward through the top plate of a pair of glass plates touching at the left end. The air between the plates acts as a thin film, and an interference pattern can be seen from above the plates. Initially, a dark fringe lies at the left end, a bright fringe lies at the right end, and nine dark fringes lie between those two end fringes. The plates are then very gradually squeezed together at a constant rate to decrease the angle between them. As a result, the fringe at the right side changes between being bright to being dark every 15.0 s. (a) At what rate is the spacing between the plates at the right end being changed? (b) By how much has the spacing there changed when both left and right ends have a dark fringe and there are five dark fringes between them?
a broad beam of
light of wavelength 620 nm is sent directly
downward through the top plate
of a pair of glass plates touching at the
left end. The air between the plates
acts as a thin film, and an interference
pattern can be seen from above the
plates. Initially, a dark fringe lies at the
left end, a bright fringe lies at the right
end, and nine dark fringes lie between
those two end fringes. The plates are
then very gradually squeezed together at a constant rate to
decrease the angle between them. As a result, the fringe at the
right side changes between being bright to being dark every 15.0
s. (a) At what rate is the spacing between the plates at the right
end being changed? (b) By how much has the spacing there
changed when both left and right ends have a dark fringe and
there are five dark fringes between them?
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