Which of the following involves the diffraction of light waves?
a. the lens of a magnifying glass makes an image look larger and upside down.
b. a glass of water acts like a prism, splitting sunlight from a window into a rainbow on the far wall.
c. light from a hallway spreads out after passing through the keyhole of a closed door.
d. a stained glass window only allows some of the light from the sun into a room.