14.4 Color and Polarization
pp. 543 - 548
Mr. Richter
Agenda (Today and Tomorrow
 Review Homework
 Introduction to Color
 Notes:
 Color
 Color and Light
 Color and Pigment
 Polarization
Objectives: We Will Be Able To…
 Recognize how additive colors effect the color of light.
 Recognize how pigments affect the color of reflected light.
 Explain how linearly polarized light is formed and detected.
Warm-Up:
 Leaves are green. What makes them green? That is, why do
we perceive them to be green?
 Discuss at your table and we will discuss as a class in a few
minutes.
Color
Introduction to Color
 The color of an object appears different
depending on the lighting conditions.
 Think about what you look like under a
black light.
 Or some jerk’s sunglasses.
 The color of an object depends on
 which wavelengths of light shine on the
object, and
 which wavelengths are reflected.
Color
 Remember, white (visible) light is
a combination or red, orange,
yellow, green, blue and violet.
 These colors each have different
wavelengths
 red = ~700 nm
 violet = ~400nm
 When light hits an object, some
wavelengths are absorbed, and
some are reflected.
Color
 An object will appear to be the color of the light that it reflects.
 Green leaves appear green because they absorb all wavelengths
of light except green, which they reflect.
 If a red light shines on a
green leaf, what color will
the leaf appear to be?
 Black!
Color
 Green objects only reflect green light.
 When white light shines on green objects (white light contains green),
green light is reflected
 When red light shines on green objects (red light contains no green),
the light is absorbed, and the object appears black.
 What color does the leaf
appear if green light shines on
it?
 Green, of course!
Color and Light
Color and Light
 A prism breaks up light into six (or
seven) distinct colors.
 These beams of light cannot be
further broken up, but they can be
put back together.
 If we add two colors of pure light
together, we can create new colors.
 This is not the same as mixing
pigments!
Color and Light
 The three primary colors of
light are red green and blue
 When two of these colors
combine, they create a
secondary color
 red + green = yellow
 red + blue = magenta
 blue + green = cyan
Color and Light (fun facts)
 The human eye can only
detect the primary colors of
light: red, blue and green.
 Everything else is a
combination of those colors.
 Visual screens like monitors
and TVs only have red, blue
and green pixels.
 The brightness of each pixel
contributes to the overall
picture color.
Color and Light: Your Turn
 A substance is known to reflect green and blue light.
 What color would it appear to be when it is illuminated by
the following colors of light?
1.
white light
2.
blue light
3.
magenta light
4.
red light
 1) cyan, 2) blue, 3) blue, 4) black
Day 2
Warm-Up
 If pure yellow light shines on a magenta
t-shirt, what color will the t-shirt appear
to an observer?
 Yellow light = green + red light
 Magenta = reflects red + blue
 Yellow shining on magenta reflects only
red light
Agenda
 Warm-Up
 Upcoming Schedule/Exam
 Notes:
 Color and Pigment
 Polarization
Upcoming Schedule
 Today: Finish 14.4
 Tomorrow: Ch. 14 Review
 Friday: Ch. 14 Test (No Quarterly Exam)
 Next Week: Refraction!
Color and Pigment
Color and Pigment
 When colors of light are mixed,
they are additive.
 Yellow light (red + green) mixed
with blue light all combine to
form white light.
 When colors of pigment are
mixed, the result is different.
 Yellow pigment mixed with cyan
pigment creates green. Why?
Color and Pigment
 When colors of pigment
mix, they are subtractive.
 Each pigment (like a paint
color) only reflects certain
colors of light.
 The more pigments are
mixed, the less light is
reflected back.
Color and Pigment
 The primary pigment colors
are:
 cyan
 yellow
 magenta
 Just like a printer cartridge.
 All other pigments are
formed from combinations
of these pigments.
Polarization
Polarization
 Light from most sources has electric and magnetic fields that
oscillate at all random angles.
 Vertical, horizontal, 7p , etc.
12
 This light is said to be unpolarized.
Polarization
 Light is polarized when the all of the electromagnetic waves
are transmitted at the same angle. Everything is aligned.
 The vibrations of the electric and magnetic fields are
parallel to each other.
Polarization
 Light can be polarized in two ways:
 Transmission: a polarizer (good word!) allows only waves of a
certain angle to pass through.
 Kind of like a picket fence.
 Reflection: most waves of light bouncing
off of a surface are polarized parallel to
that surface
 Like glare off of glass or other shiny
objects.
Polarization: Applications
 Most light we see that is polarized
due to reflection is horizontally
polarized.
 Parallel to snow covered ground, car
hoods, lakes, etc.
 Glasses and goggles are polarized
vertically to block this glare.
 Like adding a horizontal picket fence.
Wrap-Up: Did we meet our objectives?
 Recognize how additive colors effect the color of light.
 Recognize how pigments affect the color of reflected light.
 Explain how linearly polarized light is formed.
Homework
 p. 548 #1-4
 p. 552 #37-39, 41
 Chapter 14 Test Friday