Try This at Home: Rainbow Film
Nanoscale thin films can create iridescent colors by interfering with light waves.
What You Need
- a shallow pan of water
- black paper, cut small enough to fit in the pan
- clear nail polish
What To Do
1. Make sure you have an adult with you to supervise this experiment.
2. Slide the black paper into the pan so that it is completely underwater.
3. Use the brush to drip one drop of nail polish onto the surface of the water from about 4 inches up. Watch what happens.
4. Lift the paper up and out of the water so that the nail polish thin film sticks to it. Observe the thin film – does the nail polish still look clear?
5. Clean up. Let the paper dry.
The nail polish spreads out into a thin film, causing iridescent colors. Light that we see as colors has wavelengths of about 400 to 700 nanometers – billionths of a meter. The nail polish thin film is also only a few hundred nanometers thick. The film is slightly thicker in some places and thinner in others. We see different colors because light reflects differently depending on how thick the film is. Soap bubbles and oil slicks are some other examples of thin films that create iridescent colors.
Your fingernails grow approximately one nanometer every second!