Explore how to see the spectrum of light with your Optics Discovery Kit, if you haven't already done so in Submodule 2: Lenses, Mirrors, and Prisms. How do you view the spectrum with the tools at your disposal?

How could you block out some of the colors in the spectrum using the diffraction grating and other materials from your Optics Discovery Kit?

Hold one of the color filters between a light source and the diffraction grating and look through them. What do you see? Try all of the color filters in your Discovery Kit.

Which filter blocks out the most light? Which the least?

This is a picture of four color filters: red, blue, green, and yellow. Notice what's happened at the center region where all four filters have overlapped.

What "color" is in the middle? Why is this? By the end of the lesson, hopefully we'll be able to answer why.

In white light, an object that looks red, for instance, is absorbing all the other wavelengths (colors) of the white light and letting only the red reflect back to your eyes. (If you need review on wavelength of light, go back to the wavelength section of the readings.)

An object that looks black is absorbing all the wavelengths of light and allowing none (or almost none) to reflect into your eye. Then why can we see it at all, you may ask. Some of the light may reflect off the black object if it is shiny, in which case not all wavelengths are being absorbed, some are simply reflected like a mirror.

So our banana is yellow because the properties of the skin of the banana are such that it absorbs all the other colors except yellow (until, of course, it overripens and then it starts absorbing all the colors!).

What if we mix colored lights?

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