in single slit experiment explain clearly why the secondary maxima become weaker with increasing order (n) of secondary

maxima?

In single slit diffraction pattern the intensity decreases rapidly as the number of secondary maxima (n) increases. This particular topic of intensity relation is beyond the std. XII CBSE syllabus. Following treatment is given just for your knowledge. Mathematically, intensity of a particular fringe of a single slit Fraunhoffer diffraction is given by

I= I₀ (sinα/α)²

Where α = (π/λ)asinθ 

The secondary maxima condition is given by  +/- (2n+1)/2

The central maxima is given by α = 0

Thus,