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#### Investigating Special Properties of Light

Light possesses many special properties. It may be bent, reflected, diffracted, used to create optical illusions, and has a special relationship with heat. You will be investigating many of these properties through a variety of learning centers. Your teacher will already have the materials you need set up in different areas of the classroom. You and your group members will travel around the room from one learning center to the next until you have visited all of them. Make sure you take your science notebook with you so that you can record your findings.

Learning Center 1: Diffraction Action

At this center you will be using a diffraction grating to look at different colors of light. A diffraction grating works kind of like a prism in that it will separate white light into the individual colors of which it is composed.

Each color has a certain wavelength. The color red has the longest wavelength and violet has the shortest wavelength. The other colors that you might see in the spectrum are usually in this order, from longest to shortest wavelengths: red, orange, yellow, green, blue, indigo, and violet.

1. Look at each type of light that your teacher has at your center with the diffraction grating.

2. Record the colors that you see in your science notebook. For example, if only red, orange, yellow, and green are seen when you look at a flashlight beam through the diffraction grating, write this down. Also, creating a chart can help you organize your information.

Learning Center 2: Did You See The Light?

At this center you will place different objects up to a light and decide whether the object is transparent, translucent, or opaque. If it is transparent then the light will pass through it and a clear image will form. If an object is translucent, it will allow some of the light to come through, but most of the light is scattered. Thus, you can see an object through translucent material, but it will not be clear. In an opaque material, all the light is blocked so that you will not be able to see through it.

1. As you hold the objects provided by your teacher up to the light, record your findings in a chart. For example, if you held a piece of glass up to the light, you could see through it and what you would see would be clear. You would write the word "YES" in the transparent column.

What type of material would you want a computer screen to be made of: translucent, transparent, or opaque? Explain your choice.

Why would you want a flashlight bulb to be made of a transparent material?

Why would you want your sunglasses to be made of a translucent material?

What type of object, a transparent, translucent, or opaque one, would you use to make a shadow?

Learning Center 3: CD Rainbows

At this center you will be using a compact disk (CD) to look at light from several different sources.

1. Look at the surface of a CD. In your science notebook describe what the surface looks like.

2. Move the CD and try to allow some of the light from overhead to hit its surface and produce rainbow colors, or the visible spectrum. Record all of the colors that you see in your science notebook, or create a chart like you did at Learning Center 1.

3. Use the CD to look at light from a flashlight, a lamp with a 60 W bulb, sunlight from a window, and a candle. Record the colors that you were able to see in your science notebook.

4. Explain in your science notebook why you think that the CD separates light into colors and answer the following questions.

How are a CD and a diffraction grating alike?

How are a CD and a diffraction grating different?

Learning Center 4: Spinning Colors

At this center you will be creating a spinning disk that will produce different colors by adding colors together and "fooling" your eyes.

1. Use the compass to draw a circle 8 centimeters in diameter on the blank side of each of the two 3 x 5 index cards.

2. Divide each circle through the center into 8 equal wedges. On the first circle use the red and blue markers. Color every other section red and blue.

3. On the second circle use the yellow and green markers to color every other section yellow and green.

4. Cut out each of the circles. Push a pencil point through the center of the red and blue circle, and take another pencil and push the point through the center of the yellow and green circle with the colored side facing the pencil's eraser. For better balance, keep the disk down near the point end of the pencil. Put the point of the pencil on the floor and spin it like a top.

What color does the disk appear to be on the circle that you colored red and blue? Why do you think that this is so?

What color does the disk appear to be on the circle that you colored yellow and green? Why do you think that this is so?

Learning Center 5: Bending Light

At this center you will work with a partner to observe how light bends or refracts to form an image.

1. Place a penny at the bottom of a Styrofoam cup that you have cut in half. You may want to use tape to secure the penny to the center of the cup.

2. Have your partner slowly slide the cup away from you until you can no longer see the penny. Do not move. Stay in this position until your partner has completed Step 3 below.

3. Without disturbing the penny, have your partner slowly pour water into the cup until you can see the penny again. Reverse jobs and repeat the experiment.

What did you observe?

Can you explain how this is possible?

4. In your science notebook, draw the path that light takes from the penny to your eye after the water was added. You may use arrows to show what happens to the light.

Learning Center 6: The Relationship Between Light And Heat

At this center you will be studying how light and heat, which are both forms of energy, are related.

1. Take a piece of black construction paper and tape to make a cover for a thermometer.

2. Seal one end of the cover so that the thermometer does not fall out.

3. Do the same thing with a white piece of construction paper for the second thermometer.

4. Take the two covered thermometers outside and place them in full sun. Predict what you think will happen if you leave these two covered thermometers outside in full sun.

5. Wait 2 to 3 minutes and read the temperature on each of the thermometers by gently sliding them out of the cover. Record the temperature.

6. In your science notebook note whether or not your predictions were correct. Then, explain what you think happened.

7. Your teacher has prepared three cups of water and placed them outside, one in a shady spot, one in part sun/part shade, and one in full sun. Predict what you would find out if you measured the temperature of the water in these three cups. Record your predictions.

8. Take three thermometers outside, and without moving the cups, measure the temperature of the water in each cup. Record the temperatures.

9. In your science notebook note whether or not your predictions were correct. Explain why you think there was a difference in the temperatures of the three cups.

Did you know?

Some people make "sun tea." You can do this by placing a tea bag in cold water in a clear jar and covering it with plastic wrap. After the water sits for a while in the sun, it will turn from a clear color to a dark brown. Remove the tea bag, add sugar to taste, and add a little water if you need to. Add a couple of ice cubes and you have delicious iced tea.

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