Obtain the conditions for secondary maxima and minima. Also draw
the intensity distribution curve

Dear Student 
In Y.D.S.E $$\begin{gathered} when monochromatic light of wave length \lambda and silt gap is d then condition of minima and maxima will be \\ for constructive interference d\sin \theta =n\lambda \\ for constructive interference d\sin \theta =2\lambda ......1> \\ for distructive interference d\sin \theta =\frac{(2n+1)\lambda }{2} \\ for distructive interference d\sin \theta =\frac{(2\times 2+1)\lambda }{2}=\frac{5\lambda }{2}......2> \end{gathered}$$

And if you are thinking about diffraction then just reverse the cases in this the intensity goes on decreasing 

Regards