# Fresnal's biprism formula for d

1. Aug 19, 2011

### ProPatto16

1. The problem statement, all variables and given/known data

Show that the seperation of the two coherent sources is given by d=2aA(n-1) where n is the refactive index of prism.

2. Relevant equations

from youngs double slit experiment y=Rm$\lambda$/d

3. The attempt at a solution

i have no idea how to derive this formula. ive seen it many times before but nowhere shows the derivation. i can see youngs experiment is similar, but fail to see a connection?

help!

there should be a picture attached to this post. hopefully!

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2. Aug 20, 2011

### ehild

Last edited by a moderator: Apr 26, 2017