apter 5
Ch
Refraction
Predict Where to Aim a Spear
Skills Focus: observing, predicting, inferring, creating models
1. Put some water in a clear glass or clear
plastic container. Place your pencil in the
container of water so that it is leaning
toward you and is touching the bottom on
the far side of the container.
2. Look along the pencil from the top and
observe if the pencil seems bent, straight,
or in two pieces. Have your partner look
from the side of the glass. Compare your
observations. Where is the real tip of the
pencil compared to the tip you see when
looking along the pencil from the side?
3. Switch positions with your partner. Does
this make a difference in your observations?
4. For many Aboriginal fishers in British
Columbia, spearing salmon as they travel
up the rivers to spawn is an important skill.
• Predict where a person standing above
the river should aim a spear when trying
to spear a salmon: Right where the
salmon appears to be? Above the
salmon? Below the salmon? (Think of
your experience with the pencil in the
glass of water. Was the pencil point above
or below where it appeared to be?)
• Share your prediction with your
classmates. Do they agree? Be prepared
to explain your prediction.
왖 Spearing fish at Moricetown Canyon
106
NEL
Have you ever run from the beach into water? When you
run into water, your body slows down. Light also moves
more slowly through water. Light slows down when it
passes from air into a solid or liquid that is transparent
or translucent. If light enters the solid or liquid straight on,
it goes right through. If light enters the solid or liquid at
an angle (not straight), it not only slows down, it refracts.
When light refracts, it bends. Now the light travels in a
different direction. However, it will still travel in a straight
line within the solid or liquid.
Air
Glass
Air
왖 Light that enters straight on
goes right through.
Air
Glass
Ask questions as you
read. Ask yourself,
“Why is refraction
important? When does
it happen? When
doesn't it happen?”
Air
왖 Light that enters at an
angle refracts.
1. Name three materials that
would cause light to refract.
2. When is light passing through
glass or water not refracted?
3. Birds such as kingfishers and
ospreys have to look for fish
and dive down to catch
them. Think about what you
learned about refraction of
light in water. Do you think
they dive directly down or
at an angle? Explain your
answer using a diagram.
NEL
107