1. Investigating Color In the Classroom
Created for CVCA Physic By
Dick Heckathorn
29 May 2K+4 last

2. 2 Spectrum of Light
7 Mixing Colors by Addition
22 Mixing Colors by Subtraction – Define
27 Colored Filters
45 Primary Colors from C, M, Y
48 Color Printing
51 Mixing Paints
56 Physicists vs Artists
60 Illuminating Using Colored Light

3. I. The Spectrum of Light
A. White light can be separated into different colored lights called the spectrum.
1. Inv: How can a prism be used to separate white light into its component colors?
Look through a prism.
Shine ray of light into prism
Rotate prism as light passes through.

4. I. The Spectrum of Light
Demo-Disc: What does the prism do to the light?
a. Shine light from aluminum slide through a prism.
b. Block out all but red light.
c. Add second prism.
d. Mount second prism behind first.

5. I. The Spectrum of Light
How does a diffraction grating be used to separate white light into its component colors?
Look through a grating at a showcase bulb.
b. Look at spectrum using cardboard with slit on overhead and with grating fastened to overhead lens.

6. II. Mixing Colors By Addition
Different colored lights overlapping on a white surface are perceived by the eye-brain system as the additive combination of the individual colors.
1. What happens when colors of light are mixed?
a. Use ray box to observe the overlapping of light from red, green and blue filters.

7. II. Mixing Colors By Addition
b. Demonstrate: Overlap colors using projector and 3 mirrors
c. Mount color wheel on wall.

9. II. Mixing Colors By Addition
2. What happens when primary colors of light are overlapped?
R + G  ?
Yellow
R + B  ?
Magenta
G + B  ?
Cyan

10. II. Mixing Colors By Addition
3. What happens when opposite colors of light are overlapped?
B + Y  ?
White
R + C  ?
White
G + M  ?
White
When two colors are added together that produces white light, we call them complementary colors.

11. II. Mixing Colors By Addition
B. What Are Colored Shadows?
a. Look at shadows produced using red, green and blue filters with ray box first individually and then in combinations of first 2 and then 3.
b. Look at shadow produced using light from overhead or projector.
c. Look at shadow produced using two light bulbs separated by some distance.

12. II. Mixing Colors By Addition
d. Demonstrate shadows using red, green and blue bulbs individually and then in combinations of first 2 and then all three.
e. Quiz

13. II. Mixing Colors By Addition
C. Very small and closely spaced areas of color are perceived by the eye-brain system as the additive combination of the individual colors.
1. What Colors Make up a TV Screen? a. Freeze a colored video or
b. Tape of color bars from TV
Investigate using a lens.

14. II. Mixing Colors By Addition
Use a lens to view a comic strip up close?
Use a lens to view colored objects close up. (page 426 of text)
4. Use a lens to view black and white pictures in a text and/or a newspaper.

15. B -B Y White B Y + White B Y +

16. II. Mixing _______ By Addition
Different small images on a piece of paper, TV screen etc. when perceived by the eye-brain can provide very interesting results.
1. What happens when many small images are used to make a picture?
2. Does the image change when viewed from different distances? Try it.

22. Say the Color, not the Word
YELLOW
BLUE
ORANGE
BLACK
RED
GREEN
PURPLE
YELLOW
RED
ORANGE
GREEN
BLACK
PURPLE
BLUE
RED
GREEN
BLUE
ORANGE

23. Say the Color, not the Word
YELLOW BLUE ORANGE
BLACK RED GREEN
PURPLE YELLOW RED
ORANGE GREEN BLACK
BLUE RED PURPLE
GREEN BLUE ORANGE
Left – Right conflict within brain
Your right brain tries to say the color but your left brain
insists on reading the word.

24. III. Mixing Colors By Subtraction
Colored lights and colored objects can be described in terms of three attributes: hue, saturation and brightness.
The Attributes of Color
a. Hue – Main Color Name
A sensation
Saturation – Purity of Color
Rich or pale – Strong or weak
Brightness – Intensity

25. III. Mixing Colors By Subtraction
2. The color of a light source is described using the light that enters ones eyes.
3. The name of a filter is determined by the color of light transmitted when white light is incident on the filter.

26. III. Mixing Colors By Subtraction
Look through red
white  R + G + B
red  - G - B
b. Look through green
green  - R - B
c. Look through blue
blue  - R - G

27. III. Mixing Colors By Subtraction
d. Look through red and green
white  R + G + B
red  G - B
green  - R - B
Result Black
Look through red and blue
red  - G - B
blue  R - G

28. III. Mixing Colors By Subtraction
f. Look through green and blue
white  R + G + B
green  - R - B
blue  - R - G
Result Black

29. III. Mixing Colors By Subtraction
Look through cyan
white  R + G + B
cyan  - R
b. Look through magenta
white  R + G + B
magenta  - G
c. Look through yellow
white  R + G + B
yellow  B

30. III. Mixing Colors By Subtraction
d. Look through yellow and magenta
white  R + G + B
yellow  B
magenta  - G
color seen: R
Look through yellow and cyan
yellow  B
cyan  - R
color seen: G

31. III. Mixing Colors By Subtraction
f. Look through magenta and cyan.
white  R + G + B
magenta  - G
cyan  - R
color seen: B
g. Summary
yellow and magenta
yellow and cyan
cyan and magenta
Red
Green
Blue

34. III. Mixing Colors By Subtraction
2. Demonstrate what light red, green, blue, cyan, magenta and yellow filters.
transmit using:
- overhead projector
- cardboard with slit on projector
- grating over transmitted light
- colored filters in 2 x 4 cards

35. Go to Color Explanation
Click
Now

36. III. Mixing Colors By Subtraction
The primary colors for printing and painting subtraction are cyan, magenta and yellow.
Diagram for overlapping filters
yellow cyan
white 
- B 
yellow
- R =
green
(R+G+B) 
- B 
(R +G)
- R = G

37. III. Mixing Colors By Subtraction
yellow magenta
white 
- B 
yellow
- G =
red
(R+G+B) 
- B 
(R +G)
- G = R
magenta cyan
white 
- G 
magenta
- R =
blue
(R+G+B) 
- G 
(R + B)
- R = B

38. III. Mixing Colors By Subtraction
1. How is a colored pictures made?
a. Three and Four Color Printing
b. Rifle Picture
c. Picture of Garfield

39. III. Mixing Colors By Subtraction
D. The mixing of colored paints involves both additive and subtractive processes.
Predicting the resulting color is complicated because it depends on the physical properties of paints.

40. III. Mixing Colors By Subtraction
The mixing of water colors and printer inks are similar to “mixing” color filters.
Mixing pigment-based paints are not so simple.

41. III. Mixing Colors By Subtraction
Paint consists of tiny solid particles in a transparent medium.
The particles have no color or are clear with dye added.
Final result affected by
Properties of transparent medium
Density of the particles
Material on which the paint is applied

42. III. Mixing Colors By Subtraction
E. The naming of the primary colors by physicists and artists differ.
The physicists primary colors of light are:
red green blue
The physicists secondary colors of light are:
magenta cyan yellow
The artist’s calls its primary colors:
red blue yellow

43. III. Mixing Colors By Subtraction
IN PHYSICS
The physicists secondary colors of light are
magenta cyan yellow
The artist’s call their primary colors
red blue yellow
Conclusion:
Artists say red Physicists think magenta
Artists say blue Physicists think cyan

44. III. Mixing Colors By Subtraction
Demonstrate
Baggie Ad: Blue - Yellow  Green
Physicist: Cyan - Yellow  Green

45. What is the Color?
A. The color an object appears depends on the color of the illuminating light and the properties of the object.
1. What is the color of red, green, and blue on the following slide?
a. Use red, then green, and finally a blue filter to view the slide.
What is observed?

46. Red
Green
Blue

47. Red Results seen with eye. red filter  red green filter  black
blue filter  black

48. Green Results seen with eye. red filter  black green filter  green
blue filter  black

49. Blue Results seen with eye. red filter  black green filter  black
blue filter  blue

50. Red
Green
Blue

51. What is the Color?
2. What is the color of the letters made with colored magic markers?
a. Examine the letters looking first through a red filter, then a green filter, and finally a blue filter.
Describe what you see?

52. What is the Color?
3. What is the color of the letters made with colored magic markers?
a. Examine the letters when illuminated first a red light, then a green light and finally a blue light without using a color filter.
Describe what you see.

53. What is the Color? 4. Conclusion:
The colors of the letters appear the same whether
1. looking at them through a colored filter or
2. looking at them illuminated by a similar color light without using a color filter.

54. Using overhead, illuminate the following objects with
What is the Color?
Using overhead, illuminate the following objects with
Red Green Blue
light.

66. V. Are You Color Blind?
Click Here
Click Here

67. 1. What are the colors of the letters?
V. Evaluation
1. What are the colors of the letters?

68. V. Things for Thought 1. Is it a green filter?
2. What color is the baggie strips?
3. What color is the printing on
plastic?

69. That’s all folks!