Peoples Physics Concepts

16.2. Color http://www.ck12.org

16.2 Color

• Describe how our eye detects color and how color addition works.

Students will learn how our eye detects color and how color addition works. Reflection and transmission of color in
various situations is also covered.

Key Equations

Color Addition

TABLE16.1:

Red Green Blue Perceived color

X X X white

black

X X magenta

X X yellow

X X cyan

Guidance

• White light consists of a mixture of all the visible colors: red, orange, yellow, green, blue, indigo, and violet
  (ROYGBIV). Our perception of the color black is tied to theabsenceof light.


• Our eyes include color-sensitive and brightness-sensitive cells. The three different color-sensitive cells (cones)
  can have sensitivity in three colors: red, blue, and green. Our perception of other colors is made from the
  relative amountsof each color that the cones register from light reflected from the object we are looking at.
  Our brightness-sensitive cells (rods) work well in low light. This is why things look ’black and white’ at night.


• The chemical bonds in pigments and dyes –like those in a colorful shirt –absorb light at frequencies that
  correspond to certain colors. When you shine white light on these pigments and dyes, some colors are absorbed
  and some colors are reflected. We only see the colors that objectsreflect.


• Beautiful sunsetsare another manifestation of Rayleigh scattering that occurs when light travels long distances
  through the atmosphere. The blue light and some green is scattered away, making the sun appear red.