Download Light and color

Test 2 News
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Keep your Tests in your notebook but
return your Scantron forms and the
Manipulative.
Some of the questions will appear on the
comprehensive final.
Discuss questions that you missed with
your team mates.
The Plan
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Locate your name tag.
Remove the team role name and leave
it on the desk in front of you.
Leave the team name sign on the desk
as well.
Get ready to move…
Remember Attendance Sheets
EGR
Hands-on
XO
Gathers Supplies
COM
Recorder +
Chalkboard
CO
Speaks for the
Team + Attendance
Chapter 14 & 15
Light and
Color
“Inside My Eye”
Supplement
Parts of the Human Eye
(Supplement Handout)
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•
•
•
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Cornea – bends light
Iris – controls the amount of light
Pupil - opening
Lens – focuses light onto retina
Retina – back of eye
Fovea – center of your vision
Optic Nerve – “signal wire” (causes blind spot)
Blind Spot Demo (Page 265)
O
X
• Rods - brightness receptors
• Cones - color receptors
– Three Types: Red, Green, Blue
• Cones are more numerous in the center of
your vision.
• Rods are more numerous around the
periphery of your vision.
• Demo – Moving markers near periphery
Color Deficiency
Color Vision
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Colorblindness - about 10% of population
Red-green is predominant
 Yellow-blue - a few
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What is color?
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Different wavelengths of light are
perceived as different colors.
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White light contains equal amounts of
these colors. (ROY G. BIV)
Fill in the Blanks
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absorb all of the pure
Black objects _______
colors.
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reflect all of the pure
White objects _______
colors.
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transmit all of the
Transparent objects _______
pure colors.
Color Filters
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Red filters transmit red light and absorb
the other colors.
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Red objects reflect red light and absorb
the rest.
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In red light, what color do the red petals
and green leaves of rose appear?
Color Filters
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Red filters transmit red light and absorb the
other colors.
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Red objects reflect red light and absorb the
rest.
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In red light, what color do the red petals and
green leaves of rose appear?
– Answers:
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Petals appear red
Leaves appear to be black
Color Filters
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The following color filters are yours to
keep in the zip-lock bags:
– Red, Green, Blue
– Yellow, Magenta, Cyan
Flashlights
All flashlights must work for this
exercise.
Mixing Colored Light
Color Addition
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Additive Primary Colors:
Red
 Green
 Blue
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One can produce any color by varying
amplitude and mixture or red, green
and blue light.
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Color Addition Examples:
– Tiny dots called pixels on Color TV's and
Computer Monitors are colored only red,
green, or blue.
– “Color Addition”
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Lab Exercise (two pages)
– Color Addition Equations
Remember Attendance Sheets
(Role Rotation)
XO
EGR
Gathers Supplies
Hands-on
CO
COM
Speaks for the
Team + Attendance
Recorder +
Chalkboard
Lab Exercises
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“White Light” and “Color Addition Wheels”
– Everyone will color Roy G. Biv onto the 7
segment wheel.
– XO
Red + Blue = ?
– CO
Red + Green = ?
– ENG Blue + Green = ?
– COM Red + Blue + Green = ?
Mixing Colored Pigments
Color Subtraction
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Subtractive Primary Colors:
Yellow
 Magenta
 Cyan
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One can produce any color by varying
the amount of yellow, magenta and
cyan pigments.
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Color Subtraction Examples:
– Newspapers, magazines, books
– Zip-lock with colored seals
– “Color Subtraction”
 Lab
Exercise (two pages)
– Color Subtraction Equations
Color Subtraction Using
Crayons
Lab Exercise
Chromatography
Lab Exercise
Primary Colors
White
Red
Green
Blue
Yellow
Cyan
Magenta
Pure Green
Color Addition
Primary Green
Green
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Complementary Colors - any two colors
that add together to produce white
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e.g. magenta + green = white
Engineering
Astronomy
Physics
And our flag was still there...
Spiral
After Images and “Conal Fatigue”
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The human eye will see complimentary
colors after staring at a color picture.
Demos:
Colored Shapes
 Texas Flag
 American Flag
 Rose
 Lincoln
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Lab Supplement
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Color a Flag with Complementary
Colors
– Move this page forward
– What color would we use so that the
afterimage is red, white and blue?
– Write this on the supplement:
Complementary Colors
 Use cyan, black, and green get an after
image that is red, white and blue.
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Optical Illusions
Animation
Transparent and Opaque
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Transparent
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you can identify objects through it
Translucent
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(14.2)
you see diffuse light coming through it
Opaque
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you cannot see any light coming through it
Opaque objects cast shadows.
“Can Light Pass Through”
Lab Exercise
“Transparency”
Lab Exercise
“Pattern for Flashlight
Reflector Shield”
Lab Exercise
Why?
We want a point source of light rather than a beam
when we investigate the shadows created by
opaque objects.
“Tall in the Shadow”
Lab Exercise
Chapter 18
Spectra
The Electromagnetic Spectrum
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A range of light waves extending in
wavelength from radio waves to
gamma rays
The
Electromagnetic
Spectrum
On Chalkboard
The Electromagnetic Spectrum
Radio Waves
 Microwaves
 Infrared
 Visible Light
 Ultraviolet
 X-rays
 Gamma Rays
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Which form of light has the
…longest wavelength?
…highest frequency?
…highest energy?
…fastest speed?
The Electromagnetic Spectrum
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Radio Waves
Microwaves
Infrared
Visible Light
Ultraviolet
X-rays
Gamma Rays
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mnemonic
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Raging
Martians
Invade
Roy G. Biv
Using
X-rays and
Gamma Rays
Radio Waves
Microwaves
Infrared
Visible Light
Ultraviolet
X-Rays
Gamma Rays
SPF
• The SPF of a sunscreen is a laboratory measure of the
•
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effectiveness of sunscreen; the higher the SPF, the more
protection a sunscreen offers against UV-B (the
ultraviolet radiation that causes sunburn).
The SPF indicates the time a person can be exposed to
sunlight before getting sunburn with a sunscreen applied
relative to the time they can be exposed without
sunscreen.
For example, someone who would burn after 12 minutes
in the sun would expect to burn after 2 hours (120 min)
if protected by a sunscreen with SPF 10.
The Visible Spectrum
A range of light waves extending in wavelength
from about 400 to 700 nanometers.
Things that create a Spectrum
 Prism
 Raindrops
 CD’s
 Spectroscopes
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Contains a Diffraction Grating
Diffraction Grating
for Ziplock Bag
Creating a Spectroscope
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Roll up and tape black paper to form a tube.
Cover end of the tube with foil.
Use a blade to make a slit in the foil.
Temporarily tape the diffraction grating over
the other end of the tube.
Observe several light sources.
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Incandescent Light, Florescent Light, Neon Sign
Object Names
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Blue Bowl
Red Bowl
Yellow Post-it
Orange Post-it
http://sciencekit.com/
Object Names
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Red Filter
Green Filter
Yellow Filter
Cyan Filter
Gustav Kirchhoff
Robert Bunsen
“The Taste Test”
versus
“The Flame Test”
Continuous Spectra
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Hot, dense solids produce a continuous spectrum.
(All Colors)
Emission Spectra
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Hot gas produces a bright line emission spectrum.
(Bright Lines)
Absorption Spectra
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Filters behind continuous sources give
absorption spectrum.
(Missing Colors)
Example Questions
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What type of spectra do each of the following have?
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Flashlight bulb
Frosted Incandescent lamp
Neon Sign
Florescent light
Red bowl
Hot Solids
Hot Gasses
Cool objects that reflect light
Structure of the Atom
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Proton
Neutron
Electron
Energy Levels
Absorption
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When an electron is raised to a higher
energy level, the atom is said to be
excited.
Emission
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When the electron returns to a lower
energy level, energy is released in the form
of light.
“Element Fingerprinting”
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Different transitions from high levels to low
levels result in different colors of light.
Every element can be “fingerprinted” by it
spectra.
Hydrogen
Helium
Oxygen
Carbon
Every element can be “fingerprinted” by it spectra.
Matching Questions
Type of Spectrum
Appearance
1. Emission Spectra
a. All Colors
2. Continuous Spectra
b. Dark Lines
3. Absorption Spectra
c. Bright Lines
Matching Questions
1. Emission Spectra
a. Hot Solids
2. Continuous Spectra
b. Cool Solids
3. Absorption Spectra
c. Hot Gases
Incandescence
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The color of light emitted by hot glowing solids
changes with its temperature.
Glowing object colors:
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Reddish
 coolest glowing object
Orange-ish
Yellowish
White
Bluish
 hottest glowing object
Example Questions
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The star Sirius is blue and Arcturus is yellow.
Which is hotter?
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Answer: Sirius, I’m not kidding.
Consider a red filter and a blue filter. Which
is hotter?
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Answer: They should be the same temperature
because they are not “glowing”.
Fluorescence
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Some materials that are excited by
ultraviolet light can emit visible light upon
de-excitation. This is fluorescence.
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Demo - Black light and chalk
Fluorescent Lamps
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Primary excitation - electron collisions with
low pressure mercury vapor, and ultraviolet
light is given off
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Secondary excitation - ultraviolet light is
absorbed by phosphors and these emit
visible light
Phosphorescence
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Phosphorescence - a type of light emission
that is the same as fluorescence except for
a delay between excitation and deexcitation.
Electrons get "stuck" in an excited state
and de-excite gradually.
Demos - glow-in-the-dark objects
Lasers
 Laser
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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 Questions
1. Incandescence
a. mercury vapor
light tubes
2. Fluorescence
b. glow-in-the-dark
paints and plastics
3. Phosphorescence
c. light bulbs
with filaments
Matching Questions
1. 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
Law of Reflection
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“The angle of incidence equals the angle
of reflection.”
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This is true for both flat mirrors and
curved mirrors.
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Convex Mirror - security mirror
Concave Mirror - vanity mirror
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Demo: Chalk Dust and Concave Mirror
Types of Reflection
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Specular Reflection - images seen on
smooth surfaces (e.g. plane mirrors)
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Diffuse Reflection - diffuse light coming
from a rough surface (cannot see a
reflection of yourself)
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Movie
Reflection Demonstrations
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Candle in Water Video (Movie)
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Terminator II Movie
Supplemental Handouts
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Funny Face
Reverse Images
Make a Kaleidoscope
Please bring your book to class tomorrow.
EGR
Hands-on
XO
Gathers Supplies
COM
Recorder +
Chalkboard
CO
Speaks for the
Team + Attendance
Notebooks
• Due on Wednesday before the Exam.
• http://observe.phy.sfasu.edu/courses/phy
410/homework/NOTEBOOK.doc
Principle of Least Time
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Fermat's principle - light travels in
straight lines and will take the path of
least time
A
B
Wrong Path
True Path
MIRROR
Refraction
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Refraction is the bending of light when it
passes from one transparent medium to
another.
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This bending is caused by differences in
the speed of light in the media.
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WATER WAVE MOVIE
Refraction
Light Beam
Normal Line
Fast
AIR
WATER
Slow
Refraction Examples
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Light slows down when it goes from air into
water and bends toward the normal.
An Analogy: A car slows down when it
goes from pavement onto gravel and turns
toward the normal. MOVIE
Index of Refraction
n=c/v
Refraction
Observer
AIR
WATER
False Fish
True Fish
Lab Exercises
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“Refraction”
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Cup of Water and Pencil
Broken Pencil Movie
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“Finding Object Under Water”
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“Refraction Activities”
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Procedure 1 - Shallow Appearance
Procedure 2 - Spearing a Fish
Procedure 3 - Broken Images
Dispersion...
 …is
the separation of white light
into pure colors (ROY G. BIV).
 Dispersion
Examples:
Prisms
 Diffraction Gratings
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Rainbows
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Raindrops refract, reflect and disperse
sunlight.
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Rainbows will always appear opposite of
the Sun in the sky.
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You cannot run from or run to a rainbow!
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How can you make a rainbow?
Remember Attendance Sheets
(Role Rotation)
XO
EGR
Gathers Supplies
Hands-on
CO
COM
Speaks for the
Team + Attendance
Recorder +
Chalkboard
Lenses
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Converging Lens
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Diverging Lens
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A lens that is thicker in the middle and refracts
parallel light rays passing through to a focus.
A lens that is thinner in the middle than at the
edges, causing parallel light rays to diverge.
Team Exercise: Lens sorting
Myopia (Near-Sightedness)
People with near-sightedness
cannot see clearly at distance.
What kind of corrective lens will
they need?
Hyperopia (Farsightedness)
People with far-sightedness cannot
see clearly up close.
What kind of corrective lens will
they need?
“Where is the Image?”
Lab Exercise
“Making a Telescope”
Lab Exercise
Total Internal Reflection...
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…is the total reflection of light traveling in a
medium when it strikes a surface of a less
dense medium
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Demo - Laser and light pipe
Example: Optical Fiber Ring
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Laser Underwater Movie
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Woman Edge Pool Movie
Critical Angle
AIR
WATER
Total
Internal
Reflection
Light
Source
Atmospheric Refraction
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Our atmosphere can bend light
and create distorted images called
mirages.
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http://astro.sfasu.edu/movies/Highway Mirage 1.mpg

What causes stars to twinkle?

Atmospheric Turbulence
Mirage
Cool air
Warm air
Because of atmospheric refraction,
we have lingering, elliptical sunsets.
Sun
Sun
Earth
Why is the sky blue?

Nitrogen and Oxygen in our
atmosphere scatter high frequencies
of light.
Why are sunsets red?
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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?
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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
greenish blue?
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Red light is absorbed by the
molecules in the water.
Review for Test 3

Chapter 14
– Color

Chapter 15
– Refraction
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Chapter 18
– Spectra
Chapter 14
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Section 14.3 through 14.8
– Selective Reflection
– Selective Transmission
– Color Addition
– Color Subtraction
– Complementary Colors
– Conal Fatigue
– Why is the sky blue?
– Why Sunsets are Red
Chapter 15

Section 15.2 through 15.6
– Refraction - Bending
– Speed in different media
– Apparent Water Depth
– Illusions and Mirages
– Atmospheric Refraction
– Dispersion
– Rainbows
– Lenses and Telescopes
– Your Eye
– Image Formation
Exercises
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Bob the Builder and Filter Glasses
“Goggles” - Supplement
“Kaleidoscope”
“Animal Shadow”
“Prism Power”
Chromatography
Diffraction

a modification which light undergoes in
passing by the edges of bodies or through
narrow slits
…and in which the rays appear to be
deflected and to produce fringes of
parallel light and dark or colored bands
Water Wave Interference Movie
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Multiple Slit Interference Movie
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Doppler Effect
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the change in wavelength due to motion of
the source or observer
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"Wheeeeeeeeeeee…….Oooooooooooooo”
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Examples:

Water, Sound, and Light
Wavelength
Source at Rest
What happens when the source in in motion?
Movie #1
Java
Long Wavelength
Low Frequency
Low Pitch
Ooooooo!!!
Short Wavelength
High Frequency
High Pitch
Weeeeeeeee!!!
Source in Motion
As a team, describe
what happens to the
wavelength, frequency,
and pitch both in front of
and behind a moving
sound source.
Doppler Effect
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Examples:
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moving cars and trains
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Sound
Movie #2
moving buzzer in a nerf ball (in class)
Chapter 14 & 15
Light and Color
Be prepared to turn in your notebook at the beginning of Test 3.
It will be returned at the end of Test 3.
Please keep your notebook after that for your future class.
Test 3
• Everyone starts Test 3 at 1pm.
• Manipulative
– Transparent, Translucent, Opaque
– Spectra, Color, and Lenses
– Pendulum (Optional)
Remember Attendance Sheets
EGR
Hands-on
XO
Gathers Supplies
COM
Recorder +
Chalkboard
CO
Speaks for the
Team + Attendance
Remember Attendance Sheets
Your view…
XO
EGR
Gathers Supplies
Hands-on
CO
COM
Speaks for the
Team + Attendance
Recorder +
Chalkboard
Chapter 14 & 15
Light and Color
Remember Attendance Sheets
(Role Rotation)
CO
Speaks for the
Team + Attendance
COM
Recorder +
Chalkboard
XO
Gathers Supplies
EGR
Hands-on
Remember Attendance Sheets
(Role Rotation)
COM
CO
Recorder +
Chalkboard
Speaks for the
Team + Attendance
EGR
XO
Hands-on
Gathers Supplies
Remember Attendance Sheets
(Role Rotation)
CO
Speaks for the
Team + Attendance
COM
Recorder +
Chalkboard
XO
Gathers Supplies
EGR
Hands-on
Remember Attendance Sheets
(Role Rotation)
COM
CO
Recorder +
Chalkboard
Speaks for the
Team + Attendance
EGR
XO
Hands-on
Gathers Supplies