Light travels at different speeds in different mediums and can change direction when passing through a boundary. When examining the diagrams, compare them to the correct concepts described.
Light travels at different speeds in different mediums. When light passes through a boundary between media, it can change direction. The greater the difference in speeds, the more the path of light bends.
In the diagrams of solid cylinders and cubes, the flaws are likely to be related to the incorrect representation of the path of light when it changes speeds at the boundary. To identify the flaws, compare the diagrams to the correct concepts explained above.
From their source, light waves radiate outward in straight paths known as rays. Since rays cannot bend to follow a corner, they are prevented from passing through opaque objects and are unable to reach the opposite side of them. Where light is blocked, a black shadow is visible.