Were you one of the many people “tricked” by the blue and black dress that looked white and gold? Even after you knew it was blue and black did you swear it was white and gold? This activity will show you why it can sometimes be so hard to tell colors, particularly in interesting lighting.
Student Guide
Seeing Colors
Experimenting with color contrast
What colors are beads in different colors of light?
This resource was originally published in PhysicsQuest 2016: Currents.
What colors are beads in different colors of light?
- Red LED
- Green LED
- Blue LED
- Coin battery
- Beads
- Dark room
- Four sheets of white paper
- Pencil
- Tape
Intro
Before the experiment
When you look at a picture of “The Dress,” what colors do you see?
Why do you think this dress is so confusing to our eyes and brain?
What do you think it would look like in only blue light?
- Only red?
- Only green?
Setting up
Take your pile of beads and sort them into colors on a sheet of paper labeled “white light.” Draw a circle around each color category and label it with the color you see.
Connect the green LED to the battery to light the LED.
Turn off the classroom lights so that the only visible light is from the green LED.
Again, sort the LEDs into colors on a white sheet of paper labeled “green light,” using only the green light from the LED. The number of groups may be different from what you found on your “white light” paper.
Label each category with the color you see – not the color you think they are in white light, but the color you see in green light. These new colors may include gray and black.
Turn on the lights again. Write down what color beads appeared to be what colors in green light. So if you had a circle labeled “gray,” write down what color beads were in that circle when you turned on the lights.
Repeat steps 2 - 6 using the blue and red LEDs.
During the experiment
Fill out the following chart with your group. The bottom row should be the color of each bead in white light and the other rows should be the color that bead appeared in the different color LEDs.
Why do you think this dress is so confusing to our eyes and brain?
What can you say about blue beads in blue light?
- In red?
- How does this relate to the idea of colors reflecting certain colors of light?
Look at the diffraction pictures of the blue LED. What colors of light is it producing? How does that relate to the colors you “saw” when you were looking at beads in the blue light? What about the red and green LEDs?
Conclusion
In what color light do you think the blue black/white gold dress was photographed? Why?