i'm a highschool physics student trying to understand diffraction and interference etc.
I'm confused about this (in the context of the double slit experiment): if an underlying interference pattern occurs, e.g there are alternating maxima and minima all with the same intensity, how come when the single slit modulating envelope is applied and the interference pattern is subsequently shaped to the envelope, the intensity of subsidiary maxima in the double slit experiment decrease? e.g the bright dots that we see with our eyes fade as you go further out from the principle maxima. Additionally, in the attached image, are the maxima that are under the main part of the single slit envelope seen distinctly or do they blur together to give the bright central maxima that the double slit experiment produces.
Forgive my writing, it's just horribly difficult to express this question.