In Young’s double slit experiment, the upper slit is covered by a thin glass plate of refractive index 1.4 while the lower slit is covered by another glass plate having same thickness as the first one but having refractive index 1.7.
Interference pattern is observed using light of wavelength` 5400overset(@)A`. It is found that the point P on the screen where the central maximum fell before the glass plates were inserted, now has ` 3/ 4` the original intensity. It is also observed that what used to be `5^(th)` maximum earlier, lies below the point P while the`6_(th)` minimum lies above P. Calculate the thick- ness of glass plates. Absorption of light by glass plate may be neglected.