A ball with the same diameter as a light bulb is held halfway between the bulb and

Question:

A ball with the same diameter as a light bulb is held halfway between the bulb and a wall, as shown in the sketch. Construct light rays (similar to those in Figure 26.14) and show that the diameter of the umbra on the wall is the same as the diameter of the ball and that the diameter of the penumbra is 3 times the diameter of the ball.