Chp.28: Color

1
Chp.28 Color

• Agenda
• Review color reading guide
• EQs
• What is color and how do we see it?

2
Who was the first person to make a systematic
study of color and how did he carry out his
study?

• Isaac Newton
• First to make a systematic study of color
• used a prism to separate sun light into separate
  colors
• red, orange, yellow, green, blue, and violet were
  the colors he observed
• called the spread or rainbow of colors a
  spectrum

3
What is a spectrum?

• A range of some measurable quantity
• The visible light spectrum ranges from red to
  violet and includes all the colors in the rainbow
  
• ROYGBIV

4
What is the difference between black and white
light? Give two examples of white light.

• White light
• White light contains all visible frequencies of
  light
• Sunlight is a white light.
• Black
• objects appear black when they absorb all the
  light of visible frequencies
• black is not a color, it is the absence of light

5
What determines the color of visible light?

• The color of light depends on its frequency

6
What is the lowest frequency of visible light?
The highest frequency?

• red is the lowest frequency of visible light
• violet is the highest frequency of visible light

7
What are the brightest colors of visible light
and where do they appear in the visible light
spectrum? What are the least brightest colors
and where do they appear in the visible color
spectrum?

• yellow and green appear in the middle of the
  spectrum and are the brightest of all colors
• red and violet are the least bright and appear at
  either end of the color spectrum

8
What factors determine whether or not a substance
absorbs a colored light?

• Materials absorb different frequencies of light
• the natural frequency of the material determines
  what light the material absorbs
• if the natural frequency of the material matches
  the natural frequency of a certain color of
  light, they resonate and the color is absorbed

9
If a substance does not absorb colored light,
what happens when the light comes in contact
(hits) the substance?

• Light that is not absorbed is
• Passed through the material if the material is
  transparent
• reflected by the material if the material is
  opaque

10
Describe why we see different substances as
different colors. Give an example.

• Different substances have different natural
  frequencies which cause them to absorb and
  reflect different frequencies of light
• We receive and perceive the light that is
  reflected off of objects
• red rose absorbs all the colors except red, which
  is reflected back
• if the material absorbs no light, it will be the
  same color as the light that shines on it
• if the material absorbs all frequencies of light,
  it reflects none and appears black

11
What is color mixing by addition?

• The mixing of colored light
• Almost any color can be made by overlapping the
  light of three colors and adjusting the
  brightness of each color of light.

12
What are the three primary colors and why are
they important?

• Additive primary colors
• Blue, red, and green
• can be overlapped to produce the highest number
  of different colors

13
Additive Primary Colors

• Red light green light yellow
• Red light blue light magenta
• Blue light green light cyan
• Red light blue light green light white

14
What are complimentary colors? Give three
examples.

• When two colors are added together to make white
• examples
• yellow blue white
• magenta green white
• cyan red white

15
What remains if you subtract a color from white
light? Give three examples

• if you subtract a color from white light, its
  compliment remains
• white blue yellow
• white green magenta
• white cyan red

16
What are colored pigments?

• pigments are solid particles that absorb and
  reflect different frequencies of light
• pigments reflect a mixture of colors, not just one

17
What is color mixing by subtraction? Give three
examples.

• The mixing of pigments to change the color of
  reflected light

18
How is color mixing by subtraction different from
color mixing by addition?

• With color mixing by addition, the colors
  produced are made by mixing colored light
  directly from light sources.
• As you add colored light you get closer to the
  color white.
• In color mixing by subtraction you begin with
  white light and use pigments to take away
  (absorb) different colors of light and reflect
  the desired color (whats left).
• As you add pigments you get closer to black.

19
What are the three subtractive primary colors and
why are they important?

• magenta, yellow, and cyan
• three pigments most useful in color mixing by
  subtraction.
• an infinite amount of colors can be produced
  using these three colors of pigment

20
Why is a black car hotter in the summer than a
white car?

• The black car has pigments in its paint that
  absorb all the colors of visible light and
  reflect none and convert the absorbed light into
  heat.
• The white car has pigments in its paint that
  reflect all the colors of visible light and
  absorb none so no heat is generated.

21
What is a spectroscope and what is it used to do?

• instrument used to analyze the light from glowing
  elements
• When atoms in the element are excited (increase
  in energy), they give off energy in the form of
  light
• Different elements give off different frequencies
  of light
• made of a thin slit, two lenses, and a prism
  (picture pg. 437)
• Creates a line spectrum
• The spectrum seen through a spectroscope looks
  like a series of lines, not a continuous band of
  colors

22
What is a line spectrum and what does it tell us?

• Every element has its own characteristic color
• Ex- Neon gt red
• Mercury gt bluish-violet
• Helium gt pink
• Each element has a different line spectrum
• like a fingerprint
• one of the characteristics that distinguishes the
  elements from each other