Mr' Perez

1
Mr. Perez

• Grade 6 Science
• Color and Parts of the Eye

2
Parts of the Eye

• Sclera tough, white outer layer of the eye 7
• Cornea the clear layer that covers the front of
  the eye. It keeps dirt and bacteria from
  damaging the inner eye 3
• Pupil lets light enter the eye 5
• Iris controls the amount of light that enters
  the eye 6

3
Parts of the Eye

• Lens focuses light onto the retina and forms
  and upside down image on the retina 4
• Retina converts the image into electrical
  impulses, which travel to the brain 2
• Optic Nerve impulses travel along the optic
  nerve to the brain 1
• Brain images are processed in the occipital
  lobe of the brain. The brain turns the picture
  right side up

4
How Do We See?

• Light bounces off the object you are looking at,
  into the pupil.
• The light crosses your lens and the images gets
  focused.
• The object you are looking at turns upside down.
  
• The object you are looking at shines on the back
  of the eye. This part is called the retina. A
  retina contains two types of photoreceptors
  called rod cells and cone cells. Rod and cone
  cells help you to see colors and sharp details.
• The optic nerve carries the picture you see and a
  message goes to the brain.

5
Cones and Rods

• Human eyes have three types of cones, each of
  which responds to a different range of
  wavelengths
• Red cones (64) respond to mostly red (but also
  orange, yellow and green)
• Green cones (32) respond to green (but also
  yellow and blue)
• Blue cones (4) respond to mostly blue and violet
  
• Cones (7 million) are active at high light levels
  and are capable of color vision. They are used
  for day vision.
• Many animals have two cones, so they see less
  colors
• Rods (120 million) allow us to see at low light
  levels (night vision) and things appear gray at
  night
• Rods are 100 times more sensitive to light than
  cones, and you have more rods than cones

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Primary Colors of Light - RGB

• Red and green cones produce the yellow pigment
• Red and green light produce shades of yellow,
  orange, and brown
• Green and blue cones produce the cyan pigment
• Green and blue light produces shades of cyan
• Red and blue cones produce the magenta pigment
• Red and blue produces shades of purple and
  magenta
• Red, green, and blue are the primary colors of
  light (RGB - additive primaries)

7
Color Blindness

• If one or more of your sets of cones did not
  function properly, you would not be able to
  distinguish between certain colors.
• Most people who are said to be color-blind are
  not truly blind to color, but they have
  difficulty distinguishing between a few colors,
  most commonly red and green (and blue)
• Red-blind person cannot tell the difference
  between red and green
• Blue-blind person cannot tell the difference
  between blue and yellow
• Green-blind person cannot see the green part of
  the visible spectrum

8
Light and Color

• An objects color depends on the wavelengths of
  light it reflects
• You know that white light is a blend of all
  colors of visible light.
• This image shows white light striking a green
  leaf. Only the green light is reflected to your
  eyes. ROYBIV is absorbed.

9
Interpreting Color

• Why does a banana look yellow?
• The light reflected by the banana causes the cone
  cells that are sensitive to red and green light
  to send signals to your brain (that will
  interpret the color yellow)
• Red light and green light produces the color
  yellow

10
Mixing Colors

• A pigment is a colored material that is used to
  change the color of other substances. The three
  primary pigments are magenta, cyan, and yellow
  (are also called subtractive primaries)
• The color of a pigment results from the different
  wavelengths of light that the pigment reflects
• All the colors you see can be made by mixing
  three colors of light. These three colors?red,
  green, and blue?are the primary colors of light.
  Remember, you have red, green, and blue cones.
• When mixed together in equal amounts, they
  produce white light (or grey light)
• Mixing the primary colors in different
  proportions can produce the colors you see

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Primary Pigments

• You can make any pigment color by mixing
  different amounts of the three primary
  pigments?magenta (bluish red), cyan (greenish
  blue), and yellow.
• A primary pigments color also depends on the
  color of light it reflects (just like the 3
  colors of light)
• Primary pigment colors combine to produce black.
• Primary pigments absorb one of the primary colors
  of light, and create a color based on the average
  of the other two primary colors that are
  reflected back to the eye

Yellow pigment absorbs blue light, and is seen by
the eye as average of the reflected green and red
light (Figure 6)