why there is significant fall in intensity of the secondary Maxima compared to the central Maxima whereas in double slit experiment all the bright fringes are of same intensity???? Please explain this question using formulas

Solution:-It is because, the intensity of the central maximum is due to wavelets from all parts of the slit, the first secondary maximum is due to wavelets from one third part of the slit only, the second secondary maximum is due to the wavelets from the fifth part only and soon