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Question
If the separation between the slits in a Young's double slit experiment is increased, what happens to the fringe-width? If the separation is increased too much, will the fringe pattern remain detectable?
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Solution
The fringe width in Young's double slit experiment depends on the separation of the slits.
\[\chi = \frac{\lambda D}{d}\]
where
\[\lambda =\text{ wavelength}\]
\[\chi =\text{ fringe width}\]
\[D =\text{ distance between slits and screen}\]
\[d =\text{ separation between slits}\]
On increasing d, fringe width decreases. If the separation is increased too much, the fringes will merge with each other and the fringe pattern won't be detectable.
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