Science area:
Physics Concept: Light refraction
How can you break
a pencil with light?
Paradox #1
A Discrepant Event is something
that surprises, startles, puzzles, or astonishes the
observer. Often, a discrepant event is one that does not
appear to follow basic “rules of
nature” and the outcome of a discrepant event is unexpected
or contrary to what one
would have predicted.
Materials:
- 1
glass of water
- 1
pencil
Discrepancy:
If the pencil is put in the glass
of water on a slant, the pencil will not look like a whole pencil, but look as
if it is broken.
Procedure:
1. Put the pencil slantwise into the glass filled with
water.
2. Observe it from all sides.
Questions:
- What
do you see?
- What
do you see when observing the pencil from above? Eye level? From the
sides?
Explanation:
The light rays leaving the pencil
are broken at the water surface. Our eye is unaware of this, so it sees the
rays running straight forward. So we think the pencil lies in the extension of
the straight line from our eyes.
Snell’s Law:
Refraction is the bending of the path of a light wave as it
passes across the boundary separating two media. Refraction is caused by the
change in speed experienced by a wave when it changes medium.
Source:
Sandner, W. (2007) How can you
break a pencil with light? Fascination of light
Web site: http://www.fascination-of-light.net/web-lab/kids/experiment-6
