Consider the situation shown in figure-6.35. The two slits `S_(1)` and `S_(2)` placed symmetrically around the central line are illuminated by a monochromatic light of wavelength `lambda`. The separation between the slits is d. The light transmitted by the slits falls on a screen `E_(1)` placed at a distance D from the slits. The slit `S_(3)` is at the central line and the slit `S_(4)` is at a distance z from `S_(3)`. Another screen `E_(2)` is placed a further distance D away from `E_(1)`. Find the ratio of the maximum to minimum intensity observed on `E_(2)` if z is equal is : `(a) (lambdaD)/(2d) " "(b) (lambdaD)/(d)" " (c )(lambdaD)/(4d)`