Introduction:

A lot of us take color for granted; walls are colored, clothes, carpet floors, curtains. Everywhere you look there is color! But what exactly is color? Color is the way that our brain and our eyes see light.

A lot of us take color for granted; walls are colored, clothes, carpet floors, curtains. Everywhere you look there is color! But what exactly is color? Color is the way that our brain and our eyes see light.

Click here for more information about the science of color!

Purpose:

Our activity will introduce material science topics such as the electromagnetic spectrum, optics, and crystal field theory.  By relating these topics to familiar phenomena such as rainbows, bubbles, gemstones, and light bulbs we aim to communicate how the macroscopic phenomenon of color is based on more complex electronic processes occurring at a scale too small for the eye to see.

Materials:

• ¼ cup dishwashing liquid (clear is best but any color will work)
• ½ cup corn syrup (optional for increasing stability of bubbles)
• 1 cup water
• blank piece of white paper
• plastic straw
• flashlight
• darkened room
• food coloring (optional)

Materials for optional Gummy Bears and Lasers Demonstration

• Red and green gummy bears (or red and purple gummies)
• red or green laser pointer

Instructions:

Structural Color in Bubbles

1. 1. Measure out a cup of water (tap or bottled) into a measuring cup/bowl/cup that you can stir in.
2. Add ½ cup of corn syrup to the water. (If you do not have corn syrup that is okay. It is just used to stabilize the bubbles a little bit so they do not pop as quickly.)
3. Stir the corn syrup and water together until you can no longer see the corn syrup.
4. Add ¼ cup dishwashing soap and mix. Don’t stir too quickly or you will form lots of tiny bubbles.
5. Take the bubble mixture and pour it onto a plate.
6. Place one end of the straw into the bubble mixture and blow gently to create bubbles.
7. Once you have a small bubble, lift the straw gently to the middle of the bubble, making sure not to remove the straw from the bubble, and continue blowing gently. This should allow you to blow one large bubble!  It’s ok if this takes a few tries before you can blow a larger bubble.  If you find yourself unable to blow one large single bubble, the effects described above can also be observed in smaller bubbles, you just may need to look more closely!
8. Shine a flashlight onto the surface of the bubble (the flashlight on a phone works just as well!).
9. Try moving the flashlight around the bubble and observe how the colors shift. Observe the bubble over a minute or two and watch how the location of the color on the bubble changes.  Try blowing gently on the surface of the bubble and observing the effect.
10. If you are able, turn off the lights and repeat the experiment. Are the colors different?  Are they easier or harder to see?
11. Play around with the bubbles! Observe different sizes, time scales, lighting options (for example, does a regular flashlight produce the same colors as the flashlight on a phone), and anything else you can think of!
12. When you’re done, pour the bubble mixture down the sink and make sure to wash anything it was in contact with. You don’t want to leave a sticky mess for later!

Gummy Bears and Lasers Optional Activity

1. Separate out green and red gummy bears (or red and purple gummies) into two rows.
2. Take your laser pointer, being careful not to shine it in your eyes or anyone else’s eyes (including pets!!) and shine it through the red gummy bears or gummies.
3. Now, shine it through the green or purple gummies and observe the difference.

Sources:

Electromagnetic Spectrum: https://gamma-sci.com/2021/07/02/electromagnetic-spectrum-101-radio-microwave-and-infrared/

Bending of Light in Water Droplet: https://tuitionphysics.com/2016-feb/the-physics-behind-rainbow-formation/

Corundum Gem Charts: https://www.frgems.com/corundum-color-chart

Some diagrams and images adapted from PSU ChemGSA: https://sites.psu.edu/chemgsc/