Young's double slit experiment using polarised light

[Reshma]

How will the Fringe system in a Young's double slit experiment affected if,
1] a pair of polarising sheets P1 and P2, one before each of the slits S1 and S2, such that their transmission directions are parallel.

2] what will be the effect if the transmission lines are mutually orthogonal

3] in addition to the situation 2] above, one adds an analyzer A between the slits and the observation screen whose transmitting direction is at $\pi /4$ to those of P1 and P2

4] in addition to the situation in 3] one adds polariser P between light source S and P1 and P2. In what orientation of P the contrast is maximum?

 

[lightgrav]

Sounds like a College Homework Question.
in [1], do the polarizers do anything?
in [2] and later, are you presuming that
each slit does not re-polarize the transmitted light?
it seems that the only reason to have 2 slits here
is to coverge different polarizations.
Might be better to use 2 half-lenses.