The solution before revision #19885 of , by Tete. This is not the current version.
After it Changes Current version

Statement

13.4.11. What happens to the image given by the lens if the upper half of the lens is
painted over with black paint?

For problem $13.4.11$

Solution

For problem $13.4.11$
For problem

An image of the entire object will be produced albeit with reduced intensity. The intensity of the image of the middle part of the object will be reduced by exactly a half. The upper part of the object is closer to the upper part of the lens (which is painted black) and the intensity of its image will be reduced by more than a half. On the other hand, the lower part of the object is farther from the upper part of the lens, and the intensity of its image will be reduced by less than a half. (In the figure, light rays from each part of the object are evenly distributed.)

Answer

See the solution.