Primary Colors
Reflect Or Absorb?


 

Teacher Sheet(s)
ruleline
Objective:

To identify whether an object reflects or absorbs red, green, and/or blue light, and to reinforce student’s knowledge of the primary colors of light.
Level: K-4
Subjects(s): Physical Science
Prep Time: Less than 10 minutes
Duration: One class period
Materials Category: Special Requirements


 

National Education Standards
Science: 2a, 3c
Math:  
Technology (ISTE):  
Technology (ITEA):  
NGS Geography Standards:  


 

Materials:  
  • White folders or 11” x 14” poster board (One per group)
  • Flashlights (One per group)
  • 3” x 5” pieces of colored construction paper
  • Student Sheet
  • Pencil
 


 

Related Links:  

NASA site used for derivation of lesson plan:
Understanding Light
http://imagers.gsfc.nasa.gov/teachersite/UL2.htm

  


 

Pre-Lesson Instructions:  

Ask students:  "Why does the grass look green to us?"  Record their responses.  Explain to them that objects absorb and reflect the color of light we see. 

  


 

Background Information:  

The primary colors of light are red, green, and blue.  Red, green, and blue mix together to make all colors of light.  This is different than the primary colors of pigment, or paint and crayon where red, blue, and yellow make up the three primary colors.  They cannot combine to make the products of the primary colors of light.  A Venn diagram below shows the difference between the primary colors of light and primary colors of pigment.

Primary Colors of Pigment                        Primary Colors of Light

Primary colors of pigment   Primary colors of light

Objects reflect the color of light that we see and absorb all the other colors.  White objects reflect all colors of light, and black objects absorb all colors of light.   When scientists study the Earth from space, they look at the color of light reflected.  The amount of light reflected describes the characteristics of an object. 

Because the amount of light reflected can be represented by numbers, by having just the numbers, we can make an image.  Today’s analog television (TV) places color into the screen line by line.  The High Definition TV (HDTV) takes code to create the colors of the image as a whole, making a sharper and a more precise color image.

  

Guidelines:		  

1. Read the K-4 NASAexplores article, “HDTV,” and discuss it.

2.  Show the students the Venn diagrams of the colors of light and colors of pigment.  Discuss how the colors mix to make different colors.  Be sure to point out that the three primary colors of light are different that the three primary colors of pigment.  Make sure the students understand that white objects reflect all colors of light, and black objects absorb all colors of light.  

3.  Divide students into groups of three.  Give each group a flashlight, a white file folder, and five different-colored pieces of construction paper squares.  (If you use poster board, have students fold it in half, width-wise)

4.   Have groups stand their folders on the width edge.  Tell them to place an object where the sides intersect on the folder, then shine the flashlight on the object. 

5.   The students are to identify whether the object reflects or absorbs red, green, and/or blue light.  Have students complete the Student Sheet.

  


 

Discussion/Wrap-up:  
  • Review the answers of the Student Sheet.  The students should identify which of the red, green, and blue colors are absorbed and reflected for each object.  For example, for a yellow object, red and green lights are reflected while blue light is absorbed. 
  • Display a few colored objects, and ask student to identify whether it reflects or absorbs red, green, and/or blue light. 
  


 

Extensions:  
  • Have students bring in objects, such as, apples, oranges, bananas, and lemons to test how the color of light is reflected and absorbed. 
  • Have students create their own Venn diagram that demonstrates the how the colors of light mix.

 

The Color Wheel

The color wheel is one of the most important tools an artist can use. Lets take a look at how a typical color wheel is composed.


 

Primary Colors - Red, Yellow and Blue. These colors cannot be created by mixing any other colors.
Secondary Color - Orange, Green and Violet. Created by mixing two primary colors
Tertiary Color - Created by mixing a secondary color with one of it's component primary colors.
Tint - Color + White
Tone - Color + Gray
Shade - Color + Black
Value - How light or dark a color is.
Aggressive - AKA 'Warm'. The yellows, oranges, and reds. These come towards the eye more (spatially) and are generally 'louder' than passive colors.
Passive - AKA 'Cool'. The greens, blues, and violets. These recede from the eye more (spatially) and are generally 'quieter' than the aggressive colors.
Warm - see 'Aggressive'
Cool - see 'Passive'
  Before we discuss how to use a color wheel, lets take a look at some basic terms necessary for reading one properly.

 
Primary Colors
     
Red Yellow Blue


 

Secondary Colors
     
Orange Green Violet


 

Tertiary Colors
           
Yellow
Orange		 Red
Orange		 Yellow
Green		 Blue
Green		 Blue
Violet		 Red
Violet


 

Tints, Tones, and Shades
       
Base Color
(violet)		 Tint
(violet+white)		 Tone
(violet+gray)		 Shade
(violet+black)


 

Values
                   
Black 1 2 3 4 5 6 7 8 9

Notes regarding the definitions and diagrams above:

 
  • In the 'Tertiary Colors' diagram, the 'Blue Green' and 'Red Violet' are not totally accurate due to limitations of the RGB color model. They're pretty close though.

     
  • In the 'Values' diagram, only shades of gray are shown. Don't be fooled though, all colors have a value.

     
  • Regarding warm and cool colors: The definitions stated to the left are, at best, generalized. How warm or cool a color is totally dependent upon what other colors are near it. So, for example, you can conceivably have a cool yellow or a warm blue. The definitions stated hold true in most situations though.

So with the above in mind, let's move on to...

Creating Complimentary Color Schemes

A complimentary color scheme can be defined as a relationship between two or more hues on the color wheel.

It's important to note that while following the guidelines below will create a number of hues that work well together, it won't necessarily create a pleasant color scheme.
This is why you should always tweak your colors. This generally requires desaturating the basic colors (or raw hues) substantially,
and lightening or darkening some of them to create a suitable amount of contrast.

 

 
Basic compliments are defined as any two colors directly opposite each other on the color wheel.
This is the most simplistic of the four schemes shown, and is well suited for many styles of
design and more simplistic compositions for paintings, etc.

 

Examples:

   


 

   

Raw

 
   


 

   

Tweaked


 

   
Triadic compliments are defined as any three colors evenly distributed around the color wheel.
This scheme 'balances' nicely, as there is inherently a nice distribution of warms and cools.

 

Examples:

     


 

     

Raw

 
     


 

     

Tweaked


 

 
My personal favorite,
Split complimentary color schemes are very similar to the Basic scheme,
 except one of the colors is replaced by two colors, the tertiary colors to either side of it.

 

Examples:

     


 

     

Raw

 
     


 

     

Tweaked


 

 
Tetradic compliments are a little tricky. You can think of them a sort of 'double' split complimentary, where instead of only one color being replaced by the two tertiaries to either side of it, both are. Be careful with this scheme, it works well for very colorful designs, but that can be a little tricky to integrate into a functioning design/painting.

 

Examples:

       


 

       

Raw

 
       


 

       

Tweaked



Theory Vs Application (or 'How to actually make it work')
Well, theory is one thing. Making it work is frequently a whole different ball game.
Below you'll find some pointers on
how I've taken the concepts above and actually applied them.

 

  • Pay extremely close attention to your saturation. If you'll notice, all of the 'Tweaked' examples above were substantially desaturated. 'Raw' colors are, in my opinion, way too loud, especially on a computer screen.

     
  • Is color the most important aspect of a design? Kudos if you said yes, but bonus points if you said 'No, contrast is more important' ('Function' or 'Composition' would be a suitable answer too, but both are beyond the scope of this article). Anyways, point is, contrast is an extremely critical aspect of any design/painting/illustration. Without a thorough understanding of contrast as a concept, you'll have an extremely difficult time ever creating a suitable illusion of depth, and your designs will probably be either hard to read or hard to bear.

    I'll be writing a more comprehensive article on this subject shortly, but until then, just know that your designs (or paintings, or whatever) should always use a carefully weighted balance of lights and darks.
     
 

More:

Technique: colors

Primary colors Complementary colors

The photography is based on the 3 primary colors:
Red, Green and Blue
(it is system RGB)

This system is called "Additive System" :
the mixing of the 3 colors gives the white light.

This system is used for:
- slide photography
- television

The photography uses also the complementary colors:
Cyan, Magenta and Yellow
(System CMY)

This system is called " Subtractive System ":
the mixing of the 3 colors gives the darkness, the black.

This system is used for:
- print picture from negative
- ink-jet printers.

CAUTION : names and definition of the colors are OPTICS ones.

Commonly and in painting for instance :

* magenta or cyan are unknown :
- magenta = pinky red
- cyan = blue/green
- "optic" red = orange red
- "optic" blue = purple

* Subtractive System is used (mixing all the colors gives black). 
"Primary" colors in painting are complementary colors in optics :
- Red : is an optic magenta, less pink
- Blue :is an optic cyan, less green
- Yellow

In painting In optics and photo
Red + Blue = Purple Magenta+Cyan=Red
Yellow + Blue = Green Yellow + Cyan = Green
Red + Yellow = Orange Magenta + Yellow = Red

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