You use a converging lens to make a focused image on a viewing screen. A piece of cardboard is lowered just in front of the lens to cover the top half of the the lens. What happens to the image on the screen?
(a) The upper half of the image will vanish.
(b) The lower half of the image will vanish.
(c) The image will become fuzzy and out of focus.
(d) The image will become dimmer.