Question

The line width of a bright fringe is sometimes defined as teh separation between the points on the two sides of the central line where the intensity falls to half the maximum. Find the line- width of a bright fringe in a young's double slit experiment in terms of $\lambda$ d and D where the symbols have their usual meanings.

Answer 1

The line width of a bright fringe is sometimes defined as the sparation between the point on the two sides of the central line where the intensity falls to half the maximum.
$yo=\pm \frac{D\lambda }{4d}\therefore \text{LInewidth}=\frac{D\lambda }{4d}+\frac{D\lambda }{4d}=\frac{D\lambda }{2d}$