Michelson Interferometer - Fringe Shape

[cupid.callin]

Hi all

Edit: The reflecting side is the right side of left slab


Please look at the pic above ... The light from source splits at left slab and goes in 2 directions and come back to interfere.

From figure, it is obvious that path diff. in slabs for both rays is 0
and only path diff. would be because of the difference in distance of 2 mirrors from left slab, which is d

so, i found the path diff, as $\Delta = 2\mu d cos \theta \pm \frac{\lambda}{2}$

$\frac{\lambda}{2}$ as green ray is reflected by denser medium ...

But i need to know how the circular or straight fringes are formed and how it depends on alignment of M1 and M'2

Some help please ... :)

EDIT: μ would be the refractive index of stuff filled in whole system ... like air for example
and θ is incidence angle angle at slabs ... :}

 

[cupid.callin]

Some help please ?

 

[cupid.callin]

Oh come on, someone please help me !

 

[JimOlsen]

Perfectly parallel mirrors results in circles if the optics are clean. Else you get what appears to be straight lines but i believe they are just the edges of a circle.