1. the blind spot of the human eye results from a) rods attached to the retina. b) cones attached to...
TRANSCRIPT
1. The blind spot of the human eye results from
a) rods attached to the retina.
b) cones attached to the fovea.
c) a detached retina.
d) the optic nerve attached to the retina.
e) color blindness.
2. Some minerals absorb ultraviolet light and then release lower energy visible light. This process is called
a) fluorescence.
b) atomic resonance.
c) incandescence.
d) phosphorescence.
Fluorescent LampsFluorescent Lamps
• Primary excitation - electron collisions with low pressure mercury vapor, and ultraviolet light is given off
• Secondary excitation - ultraviolet light is absorbed by phosphors and these emit visible light
Phosphorescence Phosphorescence • Phosphorescence - a type of light emission
that is the same as fluorescence except for a delay between excitation and de-excitation.
• Electrons get "stuck" in an excited state and de-excite gradually.
• Demos - glow-in-the-dark objects
Lasers Lasers • Laser
– Light amplification by stimulated emission of radiation
• Lasers produce coherent light.• Coherent light means that all the light waves
have the frequency, phase and direction.• Demo - Laser and chalk dust• Demo - Laser and prism or diffraction grating
Matching QuestionsMatching Questions1. Incandescence a. mercury vapor
light tubes
2. Fluorescence b. glow-in-the-dark
paints and plastics
3. Phosphorescence c. light bulbs
with filaments
Matching QuestionsMatching Questions1. Fluorescent Lamp a. color changes
with temperature
2. Incandescent Bulb b. only one color
of light
3. Laser c. converts ultraviolet light to visible light
Chapter 13Chapter 13
ColorColor
ColorColor• Different wavelengths of light are perceived
as different colors.
• Pure Colors: ROY G. BIV
• White light contains equal amounts of these colors. (ROY G. BIV)
Selective Reflection and Selective Reflection and TransmissionTransmission
• At an interface, light can be...
• absorbed
• reflected
• transmitted
Fill in the Blanks
• Black objects _______ all of the pure colors.
• White objects _______ all of the pure colors.
• Transparent objects _______ all of the pure colors.
absorb
reflect
transmit
Color Filters• Red filters transmit red light and absorb the
other colors, etc.
• Red objects reflect red light and absorb the rest, etc.
• In red light, what color do the red petals and green leaves of rose appear?– Answer: Petal appear _____, leaves
appear to be _____.
Mixing Colored Light Mixing Colored Light Color AdditionColor Addition
• Additive Primary Colors:
• Red
• Green
• Blue
• One can produce any color by varying amplitude and mixture or red, green and blue light.
• Color Addition Example:
– Tiny dots called pixels on Color TV's and Computer Monitors are colored only red, green, or blue.
Mixing Colored Pigments - Mixing Colored Pigments - Color SubtractionColor Subtraction
• Subtractive Primary Colors:
• Yellow
• Magenta
• Cyan
• One can produce any color by varying the amount of yellow, magenta and cyan pigments.
• Color Subtraction Example:
– Newspapers and the new zip-lock sandwich bags use color subtraction.
White
Red
Green
Blue
Yellow
Cyan
Magenta
Primary Colors
Green
Pure Green
Color AdditionPrimary Green
Why is the sky blue?Why is the sky blue?
• Nitrogen and Oxygen in our atmosphere scatter high frequencies of light.
Why are sunsets red?Why are sunsets red?
• Red light is scattered the least by our atmosphere.
• The greatest path of sunlight through the atmosphere is at sunset or sunrise.
Why are clouds white?Why are clouds white?
• The color of light scattered by clusters of water molecules vary with the size of the clusters.
• The size of clusters of water molecules (droplets) vary in clouds.
Why is the ocean Why is the ocean greenish blue?greenish blue?
• Red light is absorbed by the molecules in the water.
Color VisionColor Vision• Colorblindness - about 10% of population
• Red-green is predominant
• Yellow-blue - a few
• Total - some
• Can you read this number????
• Complementary Colors - any two colors that add together to produce white
• e.g. magenta + green = white
Optical Illusions
Animation
After Images and “Conal Fatigue”• The human eye will see complimentary colors
after staring at a color picture.
• Demos:
• Colored Shapes
• Texas Flag
• American Flag
• Rose
• Lincoln
In-Class ExerciseIn-Class Exercise
1. Make a list of the seven forms of light in order of decreasing wavelength.
2. Draw a Color Addition Diagram using overlapping colored spotlights. Label all 7 colors.
3. Draw a Color Subtraction Diagram using overlapping paints. Label all 7 colors.
QuestionQuestion1. If you look at the yellow Sun just before
sunset for a few seconds and then look at a white cloud you see _______ afterimages of the Sun.
a) red
b) green
c) blue
d) cyan
QuestionQuestion2. A mixture of cyan and yellow paints gives
__________ paint.
a) green
b) red
c) black
d) white
e) blue
QuestionQuestion3. Adding red and green light gives us what
color?
a) yellow
b) cyan
c) blue
d) magenta
Suppose that two flashlight beams are shone on a white screen, one through a pane of blue glass and the other through a pane of green glass. What color appears on the screen where the two beams overlap?
a) yellow
b) green
c) cyan
d) magenta
e) red
If a car headlight emitted only yellow light, the normally green grass appears to be
a) green.
b) red.
c) black.
d) white.
e) yellow.
To see an after image of a red, white and blue Texas flag one would first stare at a flag with the complimentary colors
a) yellow, violet, and green.
b) cyan, yellow, and magenta.
c) cyan, black, and yellow.
d) yellow, cyan and green.
The worst thing that you can do for the health of a green-leafed plant is to illuminate it with only
a) red light.
b) green light.
c) blue light.
d) all are equally bad.
e) none of these.
Most of the light that we see has undergone
(a) selective interference
(b) selective transmission
(c) selective reflection
(d) selective refraction
A mixture of magenta and green lights give white light. These two colors are (a) additive primaries
(b) secondary colors
(c) complementary colors
(d) fluorescent colors
(e) interference colors
Mixing yellow paint and magenta paint gives what color?
(a) red
(b) green
(c) blue
(d) cyan
What color would red cloth appear if it were illuminated by cyan light? (a) cyan
(b) red
(c) yellow
(d) green
(e) black
• Glow in the beads
• Black Light
• Laser & Diffraction Grating
• Color Filters and Color Papers