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UNIT EIGHT: Waves. Chapter 24 Waves and Sound Chapter 25 Light and Optics. Chapter Twenty-Five: Light and Optics. 25.1 Properties of Light 25.2 Color and Vision 25.3 Optics. Chapter 25.2 Learning Goals. Explain how humans see.

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unit eight waves
  • Chapter 24 Waves and Sound
  • Chapter 25 Light and Optics
chapter twenty five light and optics
Chapter Twenty-Five: Light and Optics
  • 25.1 Properties of Light
  • 25.2 Color and Vision
  • 25.3 Optics
chapter 25 2 learning goals
Chapter 25.2 Learning Goals
  • Explain how humans see.
  • Demonstrate knowledge of the additive and subtractive color processes.
  • Apply knowledge of the behavior of light to explain why plants have certain colors.
investigation 25a
Key Question:

What happens when you mix different colors of light?

Investigation 25A


25 2 the human eye
25.2 The human eye
  • The eye is the sensory organ used for vision.
  • The retina contains light-sensitive cells called photoreceptors.
  • Photoreceptors convert light into nerve impulses that travel through the optic nerve to the visual cortex of the brain.
25 2 photoreceptors
25.2 Photoreceptors
  • The human eye has two types of photoreceptors—cones and rods.
  • Cones respond to color and rods respond to the intensity of light.
  • Rod cells “see” black, white, and shades of gray.
25 2 how we see colors
25.2 How we see colors
  • Our eyes work according to an additive color process— 3 photoreceptors (red, green, and blue) in the eye operate together so that we see millions of different colors.
25 2 making an rgb color image
25.2 Making an RGB color image
  • A television makes different colors by lighting red, green, and blue pixelsin different proportions.
  • Color images in TVs and computers are based on the RGB color model.
25 2 making an rgb color image13
25.2 Making an RGB color image
  • Like the rods and cones in your retina, a video camcorder has tiny light sensors on a small chip called a CCD.
  • There are three sensors for each pixel of the recorded image: red, green, and blue.
25 2 how objects appear to be different colors
25.2 How objects appear to be different colors
  • Your eye creates a sense of color by responding to red, green, and blue light.
  • You don’t see objects in their own light, you see them in reflected light!
25 2 subtractive color process
25.2 Subtractive color process
  • A blue shirt looks blue because it reflects blue light into your eyes.
  • Chemicals known as pigmentsin the dyes and paints absorb some colors and reflect other colors.
25 2 the cmyk color process
25.2 The CMYK color process
  • The subtractive color process is often called CMYKfor the four pigments it uses.
  • CMYK stands for cyan, magenta, yellow, and black.
25 2 why plants are green
25.2 Why plants are green
  • Plants absorb energy from light and convert it to chemical energy in process called photosynthesis.
  • Chlorophyll is the main pigment of plants absorbs red and blue light and reflects green light.
25 2 why plants are green21
25.2 Why plants are green

Plants must reflect some light to avoid absorbing too much energy.

  • A plant will die if placed under only green light!
optional investigation 25c
Key Questions:

How is the magnification of a lens determined?

What happens when you mix different colors of pigments?

Optional* Investigation 25C

Magnification and Mixing Pigments