# Teacher Activities

A partial listing of the teacher activities is contained here.

 Does Light Travel in a Straight Line? Refractive Properties of Water Creating Shadows Water Drop Magnifier Measure the Diameter of the Sun Pouring Light with Water Disappearing Glass Water Prism

### 1) Does Light Travel in a Straight Line?

Material: flashlight, 4 - 3" x 5" index cards, white supports, flexible soda straw.
1. Punch a small hole in each of the index cards at precisely the same position.
2. Stick each card into a white support to hold the card upright.
3. Place the cards about 15 cm apart with holes in a straight line.
4. Shine the flashlight so that the light travels through the hole in each card.
5. Move one of the cards a little and observe if the light passes through.

6. Now try looking through the flexible straw while it's straight at a light source at eye level.
7. Bend the straw and look at the same source.

QUESTIONS/CONCLUSIONS

1. Look down the cards when the light is passing through all the cards. Are the holes lined up in a straight line?
2. What happened when you moved one of the cards a little?
3. Can we conclude that light travels in a straight line?
4. Did you see light come all the way through the straw after you bent it?

### 2) Creating Shadows

Material: Flashlight, construction paper, scissors, popsicle stick.
1. In a darkened room shine a flashlight towards a blank wall.
2. Using your hands, see how many different sensible shapes and figures you can make.
3. Cut out some figures from construction paper and tape them to a popsicle stick.
4. Move them closer and farther away from the flashlight.

QUESTIONS/CONCLUSIONS

1. Where is it darkest in your shadow? Why?
2. What happens to your shadow when you move your hands or cutout closer and farther from the flashlight?

### 3) Measure the Diameter of the Sun.

Material: Pinhole on large dark paper, measuring stick, posterboard screen.
1. Pinhole patterns can be used to estimate sizes or distances.
2. Go outside on a clear day with a posterboard screen, measuring stick, and a pinhole on large dark paper. The pinhole may need to be made with a nail instead of a pin.
3. Put the screen on the ground, and hold the pinhole above the screen, but facing the sun. Move the pinhole towards the screen and away from it until you see a fairly clear image of the sun on the screen (the image won't be that large).
4. Measure the size of the image and the distance between the screen and the pinhole.
5. Knowing that the distance between the Earth and the Sun is approximately 1.5x1011 meters (150,000,000,000 m), calculate the diameter of the sun.

QUESTIONS/CONCLUSIONS

1. Why does the size of the image change as you move the pinhole up and down?
2. What is the relationship between the angle formed by the sun's diameter with respect to the pinhole and the angle formed by the image diameter on the screen with respect to the pinhole.
3. What method did you use to determine the diameter of the sun?
4. Compare your experimental result to the sun's diameter.

### 8) Disappearing Glass

Material: large and small glass beakers, Wesson oil, glass rod, other items made of glass.
1. Place the small beaker inside the large beaker.
2. Fill the large beaker about 3/4 full of Wesson oil. Observe what happens to the small beaker as the oil covers it.
3. Observe what happens as you place other pieces of glass into the beaker of oil.

QUESTIONS/CONCLUSIONS

1. Why do the objects disappear as they enter the oil?
2. What would happen if you used water in the beaker instead of oil?

### 9) Refractive Properties of Water

Material: Clear skinny plastic cup, pencil, empty short jar, sticker.
1. Fill cup 2/3 full with water.
2. Put the pencil in the water.
3. Look at the pencil from the top and the side.
4. Now place the sticker on a table.
5. Fill the jar completely with water and place it over the sticker.

QUESTIONS/CONCLUSIONS

1. What appears to happen to the pencil at the water level?
2. What happened to the sticker when the jar was placed over it?
3. What ideas do you have about these effects?

### 12) Water Drop Magnifier

Material: 10" long #22 bare wire, nail, water.
1. Wrap one end of the wire tightly around the nail. Twist it a couple of times so it is tight.
2. Carefully pull the wire loop off the nail. Dip it in a cup of water so that water collects in the loop.
3. Use the wire loop as a magnifier to read small letters.
4. Try to place more or less water on the loop and try to read the letters again.

QUESTIONS/CONCLUSIONS

1. Does the water in the loop act as a magnifier?
2. Does the water with more or less water behave as the better magnifier?
3. Explain why the water acts as a magnifier?
4. Is this a concave or convex lens?

### 19) Pouring Light with Water

Material: soda can, flashlight, tape, nail, water, water collector.
1. Use a can opener to take off the lid of the soda can that has the pull-tab. Clean out the inside of the can.
2. Use the nail to make a hole in the side of the soda can near the bottom of the can.
3. Put a piece of tape over the nail hole. Fill the can almost full of water.
4. Place a flashlight on top of the open can with the light pointing towards the bottom. It might be helpful to tape the flashlight in place using black electrical tape or duct tape.
5. Place the can over a dish or bucket to catch the water.
6. Turn out the room lights and turn on the flashlight.
7. Hold the can above the collector and take off the tape letting the water pour out slowly into the dish.

QUESTIONS/CONCLUSIONS

1. What do you observe happens in the stream of water?
2. Why does the light appear in the water stream?
3. Can you think of any application of this technique?

### 20) Water Prism

Material: shallow dish, mirror, white paper, light source.
1. Fill the dish almost full of water and place the mirror in the water at an angle.
2. Face the mirror towards sunlight coming through the window or use a strong source of light (slide projector or good flashlight) to shine through the water onto the mirror. Outside in full sunlight works best.
3. Put the white paper in a position to catch the reflected light. Move the paper around and at an angle until you see a rainbow of colors. You may also have to change the angle of the mirror.

QUESTIONS/CONCLUSIONS

1. Explain the order of the colors. Which ones are at the top?
2. Why do we see colors?
3. Does the mirror have to be in the water in order to see colors?
4. Does this have anything to do with rainbows that we see when it rains and the sun is shining?