Question

A concave mirror is used to form a real image of a candel. If the upper half of the mirror is covered by a piece of paper what will happen to the immage? Will it become dimmer or remain same? Why?

Answer 1

"The entire image is visible, but only at half the intensity. Each point on the object is a source of rays that travel in all directions. Thus, light from all parts of the object goes through all unblocked parts of the mirror and forms an image. If you block part of the mirror, you are blocking some of the rays, but the remaining ones still come from all parts of the object."