Are all the colors in the rainbow?

We got this question from our friend Leslie Atkins, who has posted a very detailed and helpful lesson plan guide for using this question as an activity

Where might this conversation go?

From conversations with colleagues and students, many people's first intuition seems to be a very firm "yes, all the colors are in the rainbow". However, upon further reflection it is easy to come up with interesting examples that require further scrutiny. For example, people are likely to bring up examples such as pink, brown, black, white, gray, gold, "neon green", "blue-green" and ask, "Are they really in the rainbow?"

We believe that this conversation can go in many directions. With that said, we have reason to think it is productive to use whatever examples surface as the focus of the group's discussion and inquiry, and to push the group to construct and scrutinize arguments for and against these colors as being in the rainbow as pursue the meaning and answer to the question.

Scrutiny of the examples is likely to raise lots of further questions and subsequent ideas:

• What do we mean by color? What counts as a color? What do we mean by "all" the colors?
• Are there infinite colors in the rainbow? Doesn't infinite imply all?
• What do we mean by "in" the rainbow? Even if all the colors aren't "in" the rainbow, can we use the colors in the rainbow to make any color we'd like, by mixing?
  
• Examples like pink beg the question, "What do we mean by a shade? If pink is a just shade of red (made by adding white), can we say pink is in the rainbow, because red is in the rainbow?
  
• Can we say blue-green is in the rainbow because they are next to each other in ROYGBIV. Is blue-green color just a mix of blue and green?
  
• Since black is the absence of light, maybe it's not a color. Perhaps It's no color at all. For that reason, maybe we don't need black in the rainbow to have "all the colors".
  
• We know from experience that brown can be made by mixing a lot of colors. Since many (if not all the) colors are in the rainbow, can we essentially say brown is in the rainbow?
• Others might say white (not brown) is made by mixing all the (light) colors, so white is effectively in the rainbow. But not Brown! How do you get brown light? Can you?
  
• What makes a color like "hot pink" hot, or "neon green" neon?
• Examples like gold and silver beg the question, "What makes a color metallic?" How is silver different than gray? What makes something "shiny"?
• What colors mix to make other colors? How does that work?
• What are the "primary" or "true" colors? (ROYGBIV, RBG, RBY?)
• Why do paint and light colors mix differently? Have different primary colors?
  
• How does a rainbow work?
  
• Does white light look white?
• What does frequency have to do with color? What happens when you have multiple frequencies?
  
• How do we perceive color? How does eye work?
  

Why we like this question?

We fell in love with this question right away. The questions raises lots of questions–questions we would could pursue in a unit on light and color.

People have lots of everyday experience with light and color, as well as, some academic knowledge and terminology about light and color. This question can productively bring both of those together into the same space.

There really is not a "right" answer, because it depends on how you interpret the question. Some people might think that this makes it a bad question–perhaps they see it as vague or ill-defined. We like it because it's a real concise question–one that drives people to construct clarity and definitions for what they mean.

How we decided to structure the activity:

1. 5 minute free write (to give everyone a chance to get their ideas out and be thoughtful before discussing)
   
2. 5 minute share with partner (to transition to discussion and scaffold listening through one- on-one interaction)
   
3. 20 minute class discussion (likely facilitated toward deconstructing counter examples, but open to other directions)
   

How did it go?

We asked participants at our workshop to log in to our blog and comment! See their comments.