what makes a rainbow activity and coloring page

What Makes a Rainbow? Activity + St. Patrick’s Day Coloring Page

If I told you that little bearded men dressed in green were guarding untold wealth under a bridge of refracted light, you would either lock me up in an insane asylum or elect me to public office.

But every year we celebrate a collection of folklore based on myths and legends from times when leeches made great doctors.  Silly you say?  My thoughts exactly!  So, let’s use this holiday to educate our children.  And rather than go into the genetics of tiny men, I thought a lesson on rainbows was in order.

What makes a rainbow?

A rainbow has just one ingredient.  Yup, just one.  Sunlight.  So, by definition a rainbow is 100% happiness (this coming from a year-round resident of the Pacific Northwest).

Now let’s learn about light, or more accurately light waves.  Sunlight is composed of numerous waves of different wave lengths.  The human eye can only detect wavelengths between 380 nm to 740 nm.  Wavelengths above and below this range are invisible to the human eye. 

light wave lengths
Image from NASA

This mix of waves appears to our eyes to be yellow (ish).  When this mix of light waves hits a water droplet (or a clear medium such as glass), two things happen.

  • First, the waves are refracted (or bent).  Now it is important to understand that wavelengths refract depending on length.  This means that long wavelengths bend at different angles than short wavelengths.  This angle is between 40 and 42 degrees.  This basically splits up the light into a rainbow.
  • Second, the now separated light waves reflect (bounce off) off the raindrop and back in the direction of the sun.
water droplet prims makes a rainbow
Image from NOAA

Make a rainbow challenge

There you have it!  A quick and dirty physics discussion that will make you feel better about giving your kids a coloring sheet in the name of education.

But wait, lets gets the kids outside and really learning with a challenge!

First, recap with the kids the necessary ingredients and conditions to make a rainbow.

  1. Light (sunlight works best)
  2. Water or another transparent object or medium (though there are ways to do it without transparent objects)
  3. 40 to 42-degree angle between light and observer (don’t actually measure, just note that the sun or light source generally needs to be fairly low in the sky and behind you).

Second challenge the kids to make a rainbow.  You could have them split up into groups and brainstorm or have a challenge where the first group to successfully make a rainbow wins!

Parent Guide for this Activity

Outside on clear sunny day, you can use anything that can make a mist of water.  A spray bottle, hose, or sprinkler.  Don’t tell this to the kids!  Let them think about it and solve the problem themselves.

sprinker rainbow

pattys day rainbow science coloring page

St. Patrick’s Day coloring sheet with science

After you have successfully created your rainbow, you can color this fun page showing you just how a rainbow is made.  Well…. along with a little imagination.

Or find it all in one place in our Free Membership ->

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