A convex lens forms a real image of a point object placed on its principal axis. If the upper half of the lens is painted black,
A) the image will be shifted downward
B) the image will be shifted upward
C) the image will not be shifted
D) the intensity of the image will decrease

By  painting  upper  half  of  lens,  the  focal  length  of  the  lens  will  not change,hence  the  image  will  form  on  the  same  position. But,  now  the amount  of  light  forming  image  (light  refracted  through  lens)  will  be less since half  of  the  lens  is  painted, thus,  the  image  will  be  of  low  intensity.