Two transparent sheets of thickness `t_(1)` and `t_(2)` and refractive indexes `mu_(1)` and `mu_(2)` are placed infront of the slits in YDSE setup as shown in figure-6.47. If D is the distance of the screen from the slits, then find the distance of zero order maxima from the centre of the screen. What is the condition that zero order maxima is formed at the centre O?

`[(D[(mu_(1)-1)t_(1)-(mu_(2)-1)t_(2)])/(d),(mu_(2)-1)t_(2)]`