Shadows tell us that light travels in straight lines. We can draw a ray (or streak) of light as a straight line on a piece of paper.
Can you see what’s wrong with this picture?
This is a better shadow picture. Can you see why? When was it taken, in the morning or at night?
A sundial is a clock. Some people still use them in their gardens
As the sun passes across the sky during the day, a shadow is cast of a stick in the middle of a dial, which shows the time.