# Refraction Spearfishing

```					   SNC 2P                                          Spear-Fishing Investigation         NAME: _________________________
`
SPEAR-FISHING INVESTIGATION
Light travels in straight lines through air, but does it continue to travel in straight lines when it passes from
one material to another? Look at the pictures below of the diamond, mirage, and the rainbow. What do they
all have in common? This is the question we will be investigating today.

What do these pictures have in common?
Any ideas?

Diamond                Mirage                       Rainbow

Reappearing Coin

Your grade 10 science class is planning a trip to a remote place in northern Ontario to go fishing. You think
your teacher is crazy because she says that this trip is going to show you one of the concepts you are learning
about—refraction. To make things even more bizarre, you and your classmates will be attempting spear-
fishing instead of normal fishing with a fishing rod. Because you like your teacher, you sign up for the trip.

Before you can attempt to spearfish, you are asked to complete a short activity. You will need:
Materials
1. A solid, opaque, cup (coffee mug works best).
2. A coin (penny, nickel, quarter, loonie)
3. A large beaker
4. Water
Procedure
1. Fill your beaker with water. You will need the water to pour it into the cup.
2. Place the coin in the bottom of the cup.
Step 2        Step 3
3. Move your head so an angle where the coin is just out-
PREDICT: IF the cup is filled with water,              of-sight behind the rim of the cup.
THEN the coin                                     4. Fill the cup with water without moving your head.
______________________________________                 Observe.

______________________________________
EXPLAIN: What do you think happened?

OBSERVE: What did you observe?

How did the image of the coin viewed through the water compare
to simply looking at the coin without water? Is there a size
difference?
SNC 2P                                     Spear-Fishing Investigation      NAME: _________________________

SPEAR-FISHING

In groups of 3, you will be constructing an aquarium with the appropriate tools you will need to go spear-
fishing. The following materials will be at your work stations:

Materials
1. A small empty aquarium or clear deep plastic tray.
2. A cardboard cylinder (core of a paper towel).
3. Two wire hangers
4. A piece of cardboard
5. A small washer or nut
6. Masking tape

Procedure
 Make reference to the diagram of the set-up below.
1. Fill the aquarium or clear, deep plastic tray almost full with water.
2. Hang the washer or nut on the coat hanger hook and bend the hanger such that it will hang over the
edges of the aquarium. The washer or nut should be suspended in the water. This represents your fish!
3. On the other end of the container, tape apiece of cardboard to the top edge of the aquarium or plastic
dish so that it hinges around the top edge (can be moved up or down).
4. Tape the cardboard cylinder onto the piece of cardboard hanging from the top edge of the aquarium or
plastic tray.
5. Each one of you will now get a chance to look with one eye through the cardboard cylinder and direct
it toward the washer or nut hanging in the water. Remember, you can move the cardboard to different
angles to get a good view of the washer.
6. Once you think you have found a good angle to spear the fish with, take the second piece of cardboard
(not yet used) and tape it to the cylinder and the aquarium. This will secure the cardboard cylinder in
place.
7. Take the long, straight wire (straightened from the other coat hanger) through the cardboard cylinder.
Does your “spear” hit the “fish”?
8. Take turns trying to spear the fish.
SNC 2P                                      Spear-Fishing Investigation      NAME: _________________________

Follow-up Questions and Analysis

1. Was anybody in your group successful at “spearing the fish”?

____________________________________________________________________________________
____________________________________________________________________________________
2. Where does the point of the “spear” end up in the aquarium relative to the “fish”? Is the “fish” deeper
of shallower than its image appears to be? Use a sketch to explain your reasoning.
________________________________________
________________________________________
________________________________________
________________________________________
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3. Where do we have to aim the “spear” relative to the “fish” when we go spear fishing?

____________________________________________________________________________________
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4. With the help of you notes from class and the text book, draw a diagram that shows your eye, the fish,
and how light is changing paths.

5. Was your teacher right that this would be an educational trip? What concept from the light and optics
unit did you learn more about?

____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
6. Can you think of another example that you have witnessed that illustrates the phenomenon of
refraction?
____________________________________________________________________________________
____________________________________________________________________________________
SNC 2P   Spear-Fishing Investigation   NAME: _________________________

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