a pencil using light, and find out how this illusion
- Clear Cup
the glass with water so it is about 2/3 full.
the pencil straight up and down in the glass so that
it is touching the bottom.
a look from the side. How does it look? It
probably still looks straight.
let the pencil lean to the side of the cup. You don't
need to hold it anymore. The top part of the pencil
should still be sticking out of the water.
does it look from the side this time? It's bent?!
Whoa... how did that happen?
An interesting property of light called refraction just
took place. When light enters the water, it can't move
as fast and it has to slow down slightly. It's kind of
like how if you are walking, you can walk at a normal
speed but if you walk in water, you can't walk quite
light from the image enters the water straight, then
the image looks normal - which was what you originally
did when the pencil was straight up and down. If the
light enters the water at an angle, then the change
in speed between the open air and water causes the
light beam to bend away from its original path. When
the pencil was at an angle, the image was at a bigger
angle in the water than in the air and made the pencil
look like it was bent.
can try this with other liquids and objects too. They
may refract light images differently.