33. (a) (i) A parallel beam of monochromatic light falls normally on a single slit of width 'a' and a diffraction pattern is observed on a screen placed at distance D from the slits. Explain : (I) the formation of maxima and minima in the diffraction pattern, and (II) why the maxima go on becoming weaker and weaker with its increasing number (n). (ii) Write any two points of difference between interference pattern due to double-slit and diffraction pattern due to single-slit. OR (b) (i) With the help of a ray diagram, describe the construction and working of a compound microscope. (ii) (I) The real image of an object placed between f and 2f from a convex lens can be seen on a screen placed at the image location. If the screen is removed, is the image still there ? Explain. (II) Plane and convex mirrors produce virtual images of objects. Can they produce real images under some circumstances ? Explain.