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Dr. Larry Woolf Larry.Woolf@ga sci-ed-ga (click on presentations) General Atomics Presented 1/11/05 at

You See it – But Do You Believe It? Multiple Representations and Misconceptions in Science Instructional Materials High School Science Teacher Forum for North San Diego County Teachers. Dr. Larry Woolf Larry.Woolf@ga.com www.sci-ed-ga.org (click on presentations) General Atomics

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Dr. Larry Woolf Larry.Woolf@ga sci-ed-ga (click on presentations) General Atomics Presented 1/11/05 at

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  1. You See it – But Do You Believe It?Multiple Representations and Misconceptions in Science Instructional MaterialsHigh School Science Teacher Forumfor North San Diego County Teachers Dr. Larry Woolf Larry.Woolf@ga.com www.sci-ed-ga.org (click on presentations) General Atomics Presented 1/11/05 at North County Professional Development Federation

  2. Please note: 5. I am not a teacher. 4. I have never taught students. 3. I have no conception of the life of a teacher. 2. But I have been involved in the development and review of many science instructional materials for grades 7-12 and have given ~100 workshops to teachers. 1. I have had to “teach” many of my customers (who are easily bored) when giving presentations (~20 per year).

  3. What do you or your students know about color?

  4. Let’s see what are the primary colors according to expert sources

  5. Authoritative approach Webster’s New World Dictionary: “color: the primary colors of paints, pigments, etc. are red, yellow, and blue, which, when mixed in various ways, produce the secondary colors (green, orange, purple, etc.)”

  6. The gray scale approach(neither black or white) Art Fundamentals Theory and Practice: “There are three colors, however, which cannot be created from mixtures; these are the hues, red, yellow, and blue. They are called the primary colors. A mixture of the three primaries should theoretically result in white; actually this mixture produces a neutral grey which may be considered a darkened form of white.”

  7. The 2 correct answers approach The Journal of Chemical Education: “… students should identify the three colors needed to produce all the others as red, blue, and yellow. Most artists call these the fundamental colors, The correct subtractive colors, used by printers, for example, are cyan, magenta, and yellow.”

  8. The parenthetical approach Color Printing Manual: “The primary process colors are: Yellow, Red (Magenta), and Blue (Cyan).”

  9. The loosely speaking approach Hewitt’s Conceptual Physics “For this reason, cyan, magenta, and yellow are called the subtractive primary colors. In painting or printing, the primaries are often said to be red, yellow, and blue. Here we are loosely speaking of magenta, yellow, and cyan.”

  10. What is meant by “primary colors?”

  11. What is meant by “primary colors?” • You can make “all” other colors (not really) • You can’t make a primary color by mixing

  12. Using your colored films, let’s do the experiment: Are the primary colors red, yellow, blue? • What colors can you make by mixing red, yellow and blue? • What colors can you make by mixing cyan, magenta, and yellow? • Which set of 3 produces the largest range of colors? • Can you make any of these “primary colors” by mixing? • What are likely candidates for the 3 primary colors? What cannot be the primary colors?

  13. Let’s learn more about how we see color Basic simplifying assumptions: 1. The color we see results from light of that color entering our eye. 2. This room is illuminated by uncolored (white) light

  14. Absorption of light by colored films • Place C film over color wheel on white paper • C film absorbs what color of light? • Place M film over color wheel on white paper • M film absorbs what color of light? • Place Y film over color wheel on white paper • Y film absorbs what color of light? • Place C, M, Y films on top of each other over color wheel on white paper • What happens? What does this mean?

  15. Absorption of light by colored films • Place C film over color wheel on W paper • C film absorbs R light • Place M film over color wheel on W paper • M film absorbs G light • Place Y film over color wheel on W paper • Y film absorbs B light • Place C, M, Y films on top of each other • All light (white light) is completely absorbed by the R light absorber,G light absorber, and B light absorber How can these observations be written mathematically? (R is red light, G is green light, and B is blue light and W is white light) See next page for guidance…

  16. Consider the cyan film on white paper • When cyan film is placed on white paper… • What color light do you start with? • What color of light is subtracted? • What color light remains after the subtraction? • How can you write this mathematically?

  17. Color math C W W W W – R = C

  18. Consider the magenta film on white paper • When magenta film is placed on white paper… • What color light do you start with? • What color of light is subtracted? • What color light remains after the subtraction? • How can you write this mathematically?

  19. Color math M W W – G = M

  20. Consider the yellow film on white paper • When yellow film is placed on white paper… • What color light do you start with? • What color of light is subtracted? • What color light remains after the subtraction? • How can you write this mathematically?

  21. Color math Y W W – B = Y

  22. Place cyan, magenta, and yellow films on top of each other • What happens and why? • How do you describe this mathematically and pictorially? • What does white light consist of?

  23. Color math W W – R – G – B = 0 W = R + G + B

  24. Alternate model W – R – G – B = 0 W = R + G + B

  25. Place a cyan film over a magenta film What color of light do you start with? What colors of light are subtracted? What color of light remains? How can you describe this mathematically? How can you describe this pictorially?

  26. Color math B (R +G +B) – R – G = B

  27. Now use an alternate pictorial model to show what happens:

  28. Alternate pictorial model (R +G +B) -R = G +B (G +B) -G = B

  29. What color results from these pair of colored film?

  30. What color results from these pair of colored film?

  31. What is the one big idea that determines color?

  32. What is the one big idea that determines color? • Color is determined by light absorption • More generally, students will learn in subsequent physics classes the following big idea: When light interacts with matter, it can be reflected, absorbed, or transmitted

  33. Color mixing • We found that mixing cyan and magenta films made a blue film • Mixing cyan film and yellow film makes a green film • Mixing yellow and magenta makes a red film Now let’s make a model that describes these results

  34. Color Wheel Model for Subtractive Colors Y M C What colors are between each of the subtractive primaries?

  35. Color Wheel Model for Subtractive Colors Y R G Now let’s deconstruct the model in terms of cyan, magenta, and yellow components M C B

  36. Deconstruct the model in terms of cyan, magenta, and yellow components Y R G M C Now, how could you make this “real?” B

  37. Put them together and see what happens- Do you make a color wheel?

  38. Color Wheel Model for Subtractive Colors Y R G What are the limitations of this model? Does it show all the possible colors? Does this model explain how our eyes see color? M C B

  39. A more sophisticated color model: L* a* b* color space

  40. So What? • Let’s see what color mixing is good for: • Take a look at the colored magazines using the handheld microscope • How are colored pictures made?

  41. Learning conceptually difficult subjects:From my personal reflections, experience, science education literature, and maybe this workshop, need: • Interactive learning • Learning cycle • Engage (primary colors), explore (mixing experiments), explain (color math, diagrams, wheel), extend (printing) • Converting between multiple representations • Experimental, mathematical, pictorial, graphical, model, verbal, written • Connected activities over time • Relevance to students • Underlying general scientific principles Discuss with your fellow teachers: agree or disagree?

  42. Interactive engagement vs traditional instruction • (a) "Interactive Engagement" (IE) methods are designed at least in part to promote conceptual understanding through interactive engagement of students in heads-on (always) and hands-on (usually) activities which yield immediate feedback through discussion with peers and/or instructors • (b) "Traditional" (T) courses are those reported by instructors to rely primarily on passive-student lectures, recipe labs, and algorithmic problem exams Richard Hake, Emeritus Professor of Physics, Indiana University

  43. Scientific evidence: interactive engagement is more effective than passive lecture for understanding of conceptually difficult subjects “Interactive-engagement vs traditional methods: A six-thousand student survey of mechanics test data for introductory physics courses” Richard R. Hake Department of Physics, Indiana University, From: http://www.physics.indiana.edu/~hake/

  44. Why is it hotter in the summer than the winter?

  45. Let’s now watch part of the video: “A Private Universe”

  46. “Be very, very careful what you put into that head, because you will never, ever get it out.” Thomas Cardinal Wolsey (1471-1530) From the Bad Science web site: <http://www.ems.psu.edu/~fraser/BadScience.html>)

  47. What do you think about these questions? Are the rays from the Sun ever *indirect*? Is Earth’s orbit egg-shaped? At Earth’s surface, are the Sun’s rays parallel? Can you make a scale drawing of the Earth, Sun, and Earth-Sun distance? Does the amount of atmosphere the sunlight passes through contribute to the seasons (i.e. more atmosphere to pass through in the winter so less intense sunlight)? Let’s see what the experts say …

  48. Misleading terms: “indirect rays” and “direct rays” From: A Private Universe Teacher’s Guide, p. 18

  49. Misleading terms: “indirect rays” and “direct rays” From National Geographichttp://www.nationalgeographic.com/xpeditions/activities/07/season.html “Because the direction of the Earth's tilt changes in relation to the sun, the northern and southern halves of our planet get differing amounts of sunlight over the course of the year. When the Northern Hemisphere of the Earth is leaning toward the sun, it receives direct rays of sunlight and is warmer, while the Southern Hemisphere receives more indirect rays.” “When the northern part of the Earth is leaning away from the sun, the situation is reversed—the Northern Hemisphere gets cooler, more indirect sunlight while the southern half receives direct rays. Because of this, the seasons in the Northern and Southern Hemispheres are reversed, about six months apart from each other.”

  50. Misleading use of terms contributes to misconceptions • Direct: Proceeding in a straight line or by the shortest course; straight; undeviating; not oblique • Indirect: Not direct in space; deviating from a straight line • (Also misused: “strong” and “weak” rays) All the rays from the Sun are direct rays! “Words which are used should be as close as possible to those in our everyday language, or as a minimum requirement, they should be the very same words used [by scientists]” Richard Feynman, 1965 (in Perfectly Reasonable Deviations from the Beaten Track, p.453) (these are not new thoughts!)

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