Rainbow of Colors Lesson Blog

Rainbow of Colors

How many colors are in a rainbow?

Sir Isaac Newton in 1672 first described rainbows to have 5 colors: Red, yellow, green, blue, and violet. Later he included orange and indigo, giving seven main colors by analogy to the number of notes in a musical scale, known objects in the Solar System, and the days of the week. Lucky Number 7, perhaps? The number 7 has been very significant in many ancient cultures.

Colorful Cups

Place 7 cups (I chose clear, but even a muffin tin would work) with a tablespoon of baking soda and approximately 4 drops of food coloring creating one of each color. Be careful of your ratio for indigo (4 drops blue, 2 red) and violet (2 blue, 2 red) to get a similar hue. Optional is to cover over the food coloring with another tablespoon of baking soda. Next pour approximately 25 mL of white vinegar over each. What you will see is an immediate reaction which the two substances create a carbon dioxide gas and bubble up the cup. The colors reveal instantly!

I created a card to label each of the colors and asked do you know ROY G. BIV? Well he's not real, his name makes up all the colors. An acronym to help remember.

Prism Play

Prisms are particularly peculiar. In optics, a prism is a transparent optical element with flat, polished surfaces that refract light. At least two of the flat surfaces must have an angle between them. These take some patience and best in a low lighted room with a white light source to see a rainbow outside of the prism, but for my young minds, I played "find the rainbow" as each child turns and investigates the prism.

Each color has different wavelengths. To the human eye we see the visible spectrum of each color. However, sometimes we only see some of the colors. Red (700 nanometers) has the longest wavelength and violet (400 nanometers) the shortest. Together all the colors will make white light.

Rainbow Recipe

Time to whip up a rainbow. Grab a bowl, place a CD bottom up and pour about 150 mL water. Instantly you can observe that the reflection of light changes with water. Finally hand over a flashlight and shine on the submerged CD. The rainbows amplify before your eyes. With the white light source and water you can make a rainbow. Please note that I attempted this with a traditional safety mirror and had little to no luck revealing a rainbow and this exploration had to be modified. Using the CD makes it much easier to enjoy for young children to play with a rainbow.

In Nature Rainbows are visible across the sky after it rains and the sun peeks out. The light passes through the raindrop and disperses the spectrum of colors onto the sky. This is indeed an optical illusion based from where you are standing, you view your very own rainbow. Rainbows usually are seen as half of circle because the horizon gets in the way, but at higher elevations you may see that it is actually full circle.

Rainbow Glasses

These are the best! Clear plastic covers the lens but when you put them on every light beams a rainbow of colors. Sing to the tune of "If You're Happy and you know it" with these phrases:

If you're seeing red, shake your head;

If orange is what you see, bow like a king or queen;

If you're seeing yellow, shake like jell-o;

If you're seeing green, touch your knee;

If you're seeing blue, touch your shoe;

If you're seeing indigo, wiggle your toes;

If violet is what you see, buzz like a bee!

A great book to explain how we see rainbows arc across the sky and share some special facts like what a Sun Smile is and much more can be found in the Easy-to-read Level 1 Rainbow by Marion Dane Bauer. https://www.amazon.com/Rainbow-Weather-Ready-Reads-Marion/dp/1481463365

We wrapped up with chalkart pre-writing skill: making an arc with each color on a piece of cardstock using small pieces (a quarter of 1 chalk stick). Since most colored chalk has 6 colors, they will need to overlap the blue and purple to make indigo.

This colorful class made learning the basics of rainbows and visible light so much fun!