Question

In a double slit experiment, the distance between
the slits is d. The screen is at a distance D from
the slits. If bright fringe is formed opposite to one
of the slits then its order is
​

Answer 1

The order is $\dfrac{d^2}{2\lambda\times D}$

Explanation:

Given that,

Distance between the slits = d

Distance of the screen from the slits =D

We need to calculate the order

Using formula of path difference

$\sqrt{(D^2-d^2)}-D=n\lambda$

$D(1+\dfrac{d}{D})^{\frac{1}{2}}-D=n\lambda$

$D+\dfrac{d^2}{2D}-D=n\lambda$

$n\lambda=\dfrac{d^2}{2D}$

$n=\dfrac{d^2}{2\lambda\times D}$

Hence, The order is $\dfrac{d^2}{2\lambda\times D}$

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Topic : double slit experiment

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