Question

In the young double slit experiment initially equal intensities are coming out of the two slits S and S now

Answer 1

By removing slit two you have removed a source of light to interfere with the light transmitted by the first slit. You will see simply the diffraction pattern of the first slit. Here is a word description of the mathematics: Imagine two point sources in the front focal plane of a lens. Each source will generate a plane wave traveling at an angle that is determined by the position of the point source above (or below) the optical axis of the lens. In the back focal plane of the lens you will see an interference pattern from the two plane waves produced by the two point sources. Remove one of the sources and you will be left with a plane wave traveling at an angle to the optical axis.