1. SCI 340 L51 Light and color not really in your book
This lecture takes lots of demonstration apparatus:
Transmission overhead projector with
Diffraction grating after focusing lens
Slit mask
Square mask
CMY filters
RGB filters
RGB filter wheels
Vertical-slit lamp and variac
Class set of diffraction gratings
R, G, B projectors
not really in your book

2. Today’s Objectives Explain how the human eye identifies colors.
SCI 340 L51 Light and color
Today’s Objectives
Explain how the human eye identifies colors.
Explain how colors are produced by absorption, dispersion, and scattering.

3. Electromagnetic Wave Energy
General Physics L19_EMwaves
Electromagnetic Wave Energy
Non-classical result:
E = hf
E = energy
f = frequency
h = Planck constant =  J s

4. General Physics L19_EMwaves

5. Temp Influences Spectrum
General Physics L19_EMwaves
Temp Influences Spectrum
Higher T  greater power
P/A = sT4
s = 5.6710–8 W m–2 K–4
Higher T  higher peak frequency
lmax = b/T
b = 106 nm K
Demonstrate
Vertical slit with variac, students each have diffraction grating. Show that light is dimmer and redder at lower temperatures.
Source: M. A. Seeds, Exploring the Universe

6. SCI 340 L51 Light and color
Group Work
Why do cooler objects emit a greater fraction of their energy at long wavelengths (low frequencies)?

7. How Human Color Vision Works
SCI 340 L51 Light and color
How Human Color Vision Works
424
530
560
Demonstrate
R, G, B slide projectors. Secondary colors formed from primaries, white from combination of all three.
Source: Griffith, Physics of Everyday Phenomena

8. SCI 340 L51 Light and color
Poll Question
What color do we see when green and red receptors are stimulated equally?
A. Cyan.
B. Blue.
C. Yellow.
D. Magenta.

9. SCI 340 L51 Light and color
Poll Question
What color do we see when blue and red receptors are stimulated equally?
A. Cyan.
B. Blue.
C. Yellow.
D. Magenta.

10. Bird and Reptile Color Vision
SCI 340 L51 Light and color
Bird and Reptile Color Vision
Source: Scientific American, July 2006

11. Reflection and Transmission
SCI 340 L51 Light and color
Reflection and Transmission
Demonstrate
Color filters R, G, B, C, M, Y with overhead projector slit and diffraction grating. Filters Remove colors from light.
Subtractive primary colors C, M Y with square mask and no diffraction grating on the projector. Combinations create additive primary colors and black.
(and absorption)

12. SCI 340 L51 Light and color
Poll Question
Chlorophyll absorbs blue and red light. What color does it appear?
A. red
B. yellow
C. green
D. violet

13. SCI 340 L51 Light and color
Poll Question
In color printing, which two color inks are combined to make the color orange?
Cyan and Magenta.
Cyan and Yellow.
Yellow and Magenta.
Demonstrate with CMY color wheel. Removing the C wheel still leaves a position of orange.

14. Fluorescent Light Not “Natural”
SCI 340 L51 Light and color
Fluorescent Light Not “Natural”
Source:

15. Colors Split by Dispersion
SCI 340 L51 Light and color
Colors Split by Dispersion
Source: Griffith, Physics of Everyday Phenomena, 4 ed.

16. Speed in Glass Depends on l
SCI 340 L51 Light and color
Speed in Glass Depends on l
Index of refraction
n = c/v
c = vacuum speed
v = speed in medium

17. Poll Question Which is faster in glass? Blue light. Red light.
SCI 340 L51 Light and color
Poll Question
Which is faster in glass?
Blue light.
Red light.
Both have the same speed.

18. Prism Separates White Light
SCI 340 L51 Light and color
Prism Separates White Light
Source: Griffith

19. Board Work What is wrong with this album cover?
SCI 340 L51 Light and color
Board Work
What is wrong with this album cover?

20. Dispersion Creates Rainbows
SCI 340 L51 Light and color
Dispersion Creates Rainbows
Source: Griffith

21. Primary Rainbow: 1 Reflection
SCI 340 L51 Light and color
Primary Rainbow: 1 Reflection
40°
42°
Source: Griffith, Physics of Everyday Phenomena

22. Secondary Rainbow: 2 Reflections
SCI 340 L51 Light and color
Secondary Rainbow: 2 Reflections
54.5°
52°
Source: Griffith

23. Viewing Both Rainbows Source: Ackerman and Knox, Meteorology
SCI 340 L51 Light and color
Viewing Both Rainbows
Source: Ackerman and Knox, Meteorology

24. SCI 340 L51 Light and color Why the sky is blue and sunsets are red
Rayleigh Scattering
Why the sky is blue and sunsets are red

25. SCI 340 L51 Light and color
There probably isn’t time, but this can be demonstrated nicely with a white light beam shining through dilute milk. The scattered light is bluish and the transmitted light is reddish.

26. Blue Scatters; Red Passes
SCI 340 L51 Light and color
Blue Scatters; Red Passes
Source: Griffith

27. Next Time Ray optics Ray tracing for mirrors Formulas for mirrors
Ray tracing for lenses
Formulas for lenses