if i have a laser beam then i split it into two beams with ratio 1 : 1 then i take one of them to  change its polarization angle (90) degree by passing it through an optically active substance then we make an interference between them both,  does the interference pattern change 
what i really want to understand in the above problem is.. when the two beams are  orthogonally polarized when they meet, the two electric fields (of the light beams) will be perpendicular to each other and so the magnetic fields, how can the electric field interfere with the magnetic field?