Light and Color Page 1 LIGHT AND COLOR Appendix

Transcription

1 Light and Color Page 1 LIGHT AND COLOR The Light Around Us 2 Transparent, Translucent and Opaque 3 Images 4 Pinhole Viewer 5 Pinhole "Camera" 6 The One That Got Away 7 Find the Coin 8 Cut a Pencil with Water (Part 1) 9 Cut a Pencil with Water (Part 2) 10 Flat Mirrors 11 Water Mirror 12 The Hidden Coin 13 Curvy Mirrors 14 Mirror Draw 15 Find the Magnifier 16 Concave Lenses 17 Convex Lenses 18 Fun With Prisms 19 Filters 20 Streetlamp Spectroscope 21 Spectroscopy Homework 22 How Green Is Your Blue? 23 Polarization 24 A Different Kind of Lens 25 Christmas Tree Balls 26 Appendix

2 Light and Color Page 2 The Light Around Us Materials Needed: Your thinking cap. Concepts: Sources of light. Activity: Group discussion. 1. Make a list of sources of light in your everyday life. 2. Where does the light originate? 3. Is anything else associated with the light? Further Investigation: Could you use a boxful of fireflies to warm your hands?

3 Light and Color Page 3 Transparent, Translucent and Opaque Materials Needed: Your thinking cap, roomful of "typical" objects. Concepts: Transmission of light through matter. Activity: Group discussion and demonstration. 1. Define transparent, translucent, opaque. 2. Find in the room one example each of something transparent, translucent, or opaque. 3. Why does light behave like this?

4 Light and Color Page 4 Materials Needed: Your eyes, paper. Concepts: Sources of light. Activity: Group discussion/activity. Images 1. How many objects can you find in your classroom which form images of other objects? Make a list. The image can either be a reflected or a transmitted one. 2. Characterize the image: is it upright or inverted? Is it smaller or larger than the object being imaged? 3. Can you think of other ways to classify the images or the objects which form the images? Object being imaged. Object producing image. Transmitted or reflected image? Image upright or inverted? Image larger or smaller than object?

5 Light and Color Page 5 Materials Needed: Book, piece of paper, pin. Concepts: Focusing of light by your eyes. Pinhole Viewer Activity: Use a pin to make a small hole in a piece of paper. Temporarily set the paper aside. Open up a book. Move your head close to the book, until your eyes can no longer focus the letters (probably 3 or 4 inches away). Close one eye, hold your head and the book in the same position, and try to read the page through the pinhole in your piece of paper. Explain the results.

6 Light and Color Page 6 Pinhole "Camera" Materials Needed: Large can or box, waxed paper, tape, black construction paper, thumb tack or small nail. Concepts: Light travels in straight lines. Activity: Follow this procedure to make a pinhole "camera": 1. Start with either a large coffee or juice can, shoe box, or Pringles' can. Punch a hole in the bottom (closed) end of the can or box using the thumb tack, or hammer and small nail, if necessary. The opening needs to be small enough to focus the light but large enough to let in sufficient light to see, so you may need to start with a small hole and enlarge it. 2. Cover the open end of the can with a sheet of waxed paper. Keep the paper taut and wrinkle free. Secure with tape or a rubber band. If you have the plastic lid from a Pringles' can, you can use the lid instead of waxed paper. 3. Roll a piece of construction paper around the waxed paper end of the can, with about 8 inches extending beyond the waxed paper end of the can. 4. Point the pinhole end of the can at a bright scene and view this scene by placing your eye at the paper end. You will probably have to experiment with the length of the construction paper extension to get the scene to focus on your eyes. 5. Describe what you see. Explain what you see. Use a sketch to explain. Further Investigation: Could you make this into a real camera?

7 Light and Color Page 7 The One That Got Away Materials Needed: Two identical glasses, two identical coins or paper clips, water. Concepts: Refraction of light. Activity: Put the glasses side-by-side. Put one coin in the bottom of each glass. Look straight down at the coins in the glasses. Record any observations in the space below. Fill one of the glasses with water. Record and explain your observations. Further Investigation: What does the title have to do with this activity?

8 Light and Color Page 8 Materials Needed: Shallow bowl, coin, water. Find the Coin Concepts: Refraction of light. Light doesn't always travel in straight lines! Activity: Put the coin in the bottom of the bowl. Lower yourself and your head until the coin just disappears from sight behind the rim of the bowl. Hold your head steady. Pour water into the bowl. No moving the head! What do you see? Use a drawing to explain what happened. Further Investigation: Fill in the blank: light travels in a straight line except when.

9 Light and Color Page 9 How to Cut a Pencil with Water Part 1 Materials Needed: Pencil, container with flat sides, water. Concept: Refraction of light. Activity: Fill a flat-sided container with water. Hold a pencil upright in the water and look at the pencil straight through one of the flat sides. Record your observations in the space below. Now look at the pencil, but not straight through a flat side. Record your observations in the space below. Can you explain your observations?

10 Light and Color Page 10 How to Cut a Pencil with Water Part 2 Materials Needed: Pencil, glass with round sides, water. Concept: Refraction of light. Activity: Fill a glass with water. Put a pencil in the water. Observe the pencil with your eyes at the level of the water. Look at the pencil from positions all around the glass. Record your observations in the space below. Did you notice anything different from "How to Cut a Pencil with Water, Part 1?" If you did, can you explain the difference?

11 Light and Color Page 11 Flat Mirrors Materials Needed: Flat mirrors, pencil, clothespins. Concepts: Reflection of Light. Activity: 1. Look at yourself in a flat mirror. What do you see? Explain. A diagram might help. 2. Use two clothespins to stand two flat mirrors upright on the table with a right angle between them. Hold a pencil between the two mirrors. What do you think you will see. What do you see? Further Investigation: If a mirror reverses the image from left to right, why doesn't it also reverse the image from up to down.

12 Light and Color Page 12 Water Mirrors Materials Needed: Transparent glass, water, shiny object (like a spoon). Concepts: Another way to make a mirror. Activity: Fill a transparent glass part way with water. Place a spoon or other shiny object in the glass. Place the glass near the edge of the table. Get down and look up from below at the bottom of the surface of the water. What do you see? Further Investigation: Is there anything interesting that you see about the size/shape of the object in the water. Is there anything interesting that you don't see? Explain.

13 Light and Color Page 13 The Hidden Coin Materials Needed: Clear glass, coin, index card, water. Concepts: Refraction of light. Light doesn't always travel in straight lines! Activity: 1. Put the coin underneath the empty glass. 2. Put an index card on top of the glass (the index card is only used to keep you from looking straight down at the coin). Can you see the coin? 3. Now pour water into the glass while you continue watching the coin from the same position as in the last step. (You might want to move the index card while you pour!) What do you observe? Further Investigation: Fill in the blank: light travels in a straight line except when.

14 Light and Color Page 14 Curvy Mirrors Materials Needed: Concave mirror, convex mirror. A large shiny spoon can be used for both of these mirrors. Concepts: The images of objects when viewed in curved mirrors. Activity: The convex mirror is the one that curves away from you, like the bottom of a spoon. The concave mirror is the one that curves toward you, like the bowl of a spoon. 1. Hold the convex mirror several feet away from you and view the reflection of your face. You may have to close one eye to get your image focused. What do you see? Now move the mirror closer. What happens? Move the mirror very close to your face. What do you see. Describe your reflection at different mirror distances-- larger or smaller than life, upright or inverted? 2. List some of the places where a convex mirror is used. 3. Repeat step (1) with the concave mirror. 4. List some of the places where concave mirrors are used. Further Investigation: Explain the funny mirror at McDonald's. Can you make a funny mirror out of your flexible "flat" mirrors?

15 Light and Color Page 15 Mirror Draw Materials Needed: Flat mirror, pencil and paper, book, clothespin. Concepts: Reversal of the image on reflection from a mirror. Hand-eye coordination. Activity: 1. Draw some figures on the paper. Make sure the dimensions of the figures are less than the width of the mirror. Draw a simple figure with straight sides. Draw a more complex figure with straight sides, such as a pointed star. Draw a curvy figure, such as your name written in cursive. 2. Use your clothespin or prop the flat mirror against a book to make it stand vertical. Do this on your paper close to the figures. 3. Sit in a position where you can see the figures on the paper and the reflections of the figures in the mirror. 4. Take another book and place it on the sheet of paper so that you block your view of the figures on the paper but not in the mirror. 5. Place your pencil at some point on the figure on the paper and trace the figure by looking only at the reflection. Do this with the straight line figures first and move up to curved figures when you get good at it. Can you do it? Try the maze to the right.

16 Light and Color Page 16 Find the Magnifier Materials Needed: Classroom items, your imagination. Concept: How to make a lens. Activity: How many objects in the room can you find that will produce a magnified image of another object? I will count "shrink" as well as "enlarge" to both qualify as "magnify." Do all of the magnifiers you found have any characteristics in common? This activity used to be called "Water Drop Microscope." Here are the instructions for the old activity: "Make a loop of copper wire by winding it around a nail. Dip the loop in water and look through it. What do you see. Explain how the water drop acts as a magnifying lens. Sometimes you can tap off most of the water and make another kind of lens." This activity never worked particularly well. Further Reference: UNESCO. 700 Science Experiments for Everyone. New York: Doubleday, 1958.

17 Light and Color Page 17 Materials Needed: Concave lens. Concept: Images formed by concave lenses. Concave Lenses Activity: A concave lens is also called a diverging lens. Handy mnemonic: when you look at a concave lens, it is "caved in" away from you. Do the following activities with your concave lens. 1. Look at a very distant object or scene. Describe the image formed by the lens. Is it erect or inverted? Is the image smaller or larger than the object? 2. Look at a very close object. Describe the image formed by the lens. Is it erect or inverted? Is the image smaller or larger than the object? 3. Can you look at an object through the lens and find a position from which the object is inverted or enlarged? If so, describe the position of the object relative to the lens.

18 Light and Color Page 18 Materials Needed: Convex lens, ruler. Concepts: Images formed by convex lenses. Convex Lenses Activity: A convex lens is called a converging lens. It is thicker in the middle than on the edges. Do the following activities with your convex lens. 1. Find the focal length of the convex lens. Do this by placing the lens at a large distance from a bright object (such as overhead lights) and close to a piece of paper or other flat surface. Move the lens away from or towards the paper until the object comes to a focus. The distance from the paper to the lens is the focal length. 2. Try to read a book through the lens, with the book closer to the lens than the focal length. Describe the image seen through the lens. Larger or smaller than the book type? Upright or inverted? 3. Look at a distant object about through the lens. You will probably have to move the lens back and forth to make the object sharp instead of blurry. Describe the image of the object. Larger or smaller than the object? Upright or inverted? 4. Can you look at an object through the lens and find a position from which the object is inverted and enlarged? If so, describe the position of the object relative to the lens. 5. If the envelope your lens came in gives a focal length, compare the listed focal length with the focal length you obtained in part 1 above.

19 Light and Color Page 19 Fun With Prisms Materials Needed: Sunlight, prism, white paper. Concept: Separation of light into colors. Activity: Place a piece of white paper in bright sunlight. Let the sun shine through the large side of the prism onto the paper. Move the prism around until you see a "rainbow" on the paper. Explain why you see the colors. Light rays bend when they pass through the prism. Different colored light rays, a and b for example, are bent through different angles. The result is a color spectrum. Light undergoes total internal reflection (see explanation in "Water Mirrors" activity) in a 45 prism. That makes such a prism useful in applications like binoculars. The reflection is total; much better than mirrors can produce.

20 Light and Color Page 20 Filters Materials Needed: Red, blue, and green filters, white paper, colored pens or crayons, a prism. Concept: Filters transmit only certain colors. Activity: Make some simple single-color drawings (red, orange, yellow, green, blue, purple). Look at the drawings through a filter. Fill in the colors of the drawings as seen through the filters in the table below. Can you draw any conclusions? Filter Drawing Red Blue Green red orange yellow green blue purple Now repeat the "Fun With Prisms" activity, except hold the colored filters between the prism and the paper. What do you observe? Do your observations match your conclusions from viewing the drawings through the filters?

21 Light and Color Page 21 Streetlamp Spectroscope Materials Needed: Toilet paper or paper towel tube, diffraction grating (what's that?), tape and scissors, black construction paper. Concept: The cheapest commercial spectroscope costs about $1.00. We can make one almost for free. Activity: 1. Cut two squares from the black construction paper. The size of the squares should be a little larger than the diameter of the cardboard roll. 2. Cut off a small rectangular piece of your diffraction grating (e.g. 5/8"x1/2"). 3. Cut a hole in the middle of one of the construction paper squares. The dimensions of the hole aren't critical, as long as the hole is just smaller than the piece of diffraction grating you cut in step 2 above. Either a round hole or a rectangular hole will work. I prefer the rectangular hole. 4. Tape the diffraction grating over the hole you just cut, but make sure that no tape covers the hole. Tape the construction paper with the diffraction grating to one end of the tube, with the diffraction grating centered on the tube. 5. Cut a slit approximately 1/8 inch wide and an inch or so long in the other piece of construction paper. The dimensions aren't critical but the slit needs to have sharp edges. 6. Hold the tube up and look through it at a light. The end with the diffraction grating should be closest to your eye. Hold the slit against the other end of the tube. Rotate the tube, keeping the slit fixed, until you see a color spectrum. Tape the slit securely to the tube in this orientation. Further Investigation: How does this work? Why do I prefer the rectangular grating end? Why do I need the tube at all?

22 Light and Color Page 22 Spectroscopy Homework Materials Needed: Streetlamp spectroscope, light sources. Concepts: Different light sources produce different colors in their spectra. The spectra can be used to identify the light sources. Activity: 1. Search your hometown for lights which produce spectra identical to those of one or more of the lights you viewed in the "Streetlamp Spectroscope" activity. I know of one match for sure in Rolla, and I have been told about another, but have never had a spectroscope with me when I passed this particular light source. Record the results of your search below or on the back of this page. Use a description or a sketch. 2. Search your hometown for lights which produce other interesting spectra. Record the results below or on the back. Use a description or a sketch. 3. I will check up on you another day. Further Investigation: How could this technique be useful to scientists? Can you think of any variations on this kind of detective work?

23 Light and Color Page 23 How Green Is Your Blue Materials Needed: Filters, spectroscope, bright white light. Concepts: Filters transmit only a particular color or colors. Activity: Fill in the blank: white light is made up of. 1. Find a good source of white light. An ordinary lamp bulb is OK. Sunlight reflected off white paper works extremely well. 2. Look at the light through your spectroscope. What do you see? 3. Look at the light through your spectroscope. Carefully move a colored filter in front of the spectroscope without disturbing your line of sight. Fill in the following table. Filter(s) Observation 1 red 2 red 1 green 2 green 1 blue 2 blue 4. Answer this question: how green is your blue filter? Can you explain what is going on here?

24 Light and Color Page 24 Polarization Materials Needed: Two squares of polarizing material, LCD watch or calculator. Concepts: Polarization of light. Activity: 1. Look through one of the squares at one of the overhead lights in the room. Rotate the square and describe what happens. 2. Look through one of the squares at the reflection of the overhead lights. Rotate the square and describe what happens. 3. Look through two of the squares at the overhead lights. Rotate one of the two squares and describe what happens. 4. Look through one of the squares at the LCD display of a watch or calculator. Rotate the square and describe what happens. 5. Place a square in front of each eye and rotate them until your have "polaroid sunglasses." Do not look at the sun with polaroid sunglasses. 6. Make a list of places where polaroid material may be used.

25 Light and Color Page 25 Materials Needed: Fresnel Lens. Concept: This is another way to make a lens. A Different Kind of Lens Activity: Take the large transparent piece of plastic out of its plastic pouch. What is it? What does it do? How does it work? Have we seen anything else like it today? Further Investigation: Can you find anything else in your school which uses an object such as this? What other uses are there for such objects?

26 Light and Color Page 26 Christmas Tree Balls Materials Needed: Christmas tree balls, the bigger the better, and silver is best. Concept: Activity: