We see light because it stimulates cells in our eyes. This stimulation is an example of light’s ability to influence chemistry. And because our eyes are able to distinguish among the different wavelengths of light, we perceive colors. Sunlight normally appears uncolored because it contains a rich mixture of wavelengths that our eyes interpret as whiteness. However, there are situations in which sunlight becomes separated into its constituent colors.
You can observe this separation of colors by looking at sunlight passing through a cut crystal glass or bowl, or by reflecting sunlight from a CD or DVD. Hold the object in direct sunlight and observe the light that it redirects toward your eyes or projects onto a white sheet of paper nearby. While some of the light you see will still be white, you should see colors as well.
Turn the object slowly in your hand and observe how the colors change. You will see gradual progressions from one color to the next.
- What should that sequence of colors be?
- How does this sequence relate to the colors of the rainbow?
- What is the relationship between this sequence and the wavelengths of light?
- Can you get some sense for the relative wavelength spacings of the classic rainbow colors: red, orange, yellow, green, blue, indigo, and violet? Estimate them here.
- Why do you think this works with the object you are using (glass, crystal, CD, etc.) and not something like a white sheet of paper?
- Find an interesting transparent material in your house (maybe a piece of jewelry, an antique, something from the garage, or even an oil from the kitchen). What did you use and did it also show you the colors of the rainbow as well? Why do you think this did or didn’t work?
Concluding Everyday Life Task:
7.Name two examples from your personal daily life where you see a phenomenon like this. Please try not to give standard examples as given in the textbook but make it a personal challenge to discover new examples in your daily life!
