Hi! plz help me in the following problem? "The electric field at point P due to N slits is, E (r, theta, t) = A(r) sin N delta phi/2 cos(kr-wt) _____________ sin delta phi/2 where delta phi=kdsin (theta) , "d" being the spacing between the adjacent slits. let N=4 (a) Find two angles on either side of theta=0 at which there is an interference minima. (b) Find the spacing between the minima compare to the case of only two slits of separation "d". Now i have solve its (a) part but i just cant solve its (b) part. Can u plz help me in this plzzzzzzzzzzzzzzzzz. Thanks in advance!