(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

When the system is in air

## d \sin {\theta} = n \lambda ## .....(1)

When the system is in water and slit separation is 2d,

## \mu 2d \sin {\theta} = n \lambda ## .....(2)

## \tan {\theta} = \frac y D ## .....( 3)

Taking d<<D, ## \tan {\theta} \approx \sin {\theta} ## .....(4)

## \frac { n \lambda }{ 2 \mu d} = \frac { y} D ## .....(5)

## y = \frac { n \lambda D }{ 2 \mu d} ## .....( 6)

Fringe width ## = \frac { \lambda D }{ 2 \mu d} ## .....(7)

Now, ## \frac { \lambda D}{ d} =s ## .....( 8)

Fringe width ## = \frac { s }{ 2 \mu } = \frac { 3s} 8 ##

So, the correct option is (e).

Is this correct?

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# Homework Help: Interference fringe width

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