Submodule 2: Lenses, Mirrors, and Prisms: Objective 1
Steve Beeson, Arizona State University

How would you break up white light into a spectrum?

Do any of the objects in your Optics Discovery Kit make a rainbow? Try looking through some of them at a light source.

The slide-looking piece is called a diffraction grating, a piece of plastic which has many tiny grooves etched into it which separate white light into its component colors.

Are there other optical elements from your Discovery Kit that might make a spectrum of colors?

Use your flashlight with a piece of paper over the front (with a small slit cut in the paper) to make a small beam of light. Shine this beam on the prism in your Kit and let the refracted beam fall on a piece of white paper. What do you find?

Isaac Newton first saw a spectrum in this way in 1672 when a stray beam of sunlight in his darkened room happened to land on a prism.

Prisms are often the easiest way to see a spectrum, since many different objects can sometimes act like prisms. Raindrops or a glass of water, for instance, can act like a prism and disperse light into its color spectrum.

Light & Optics
Submodule 2
PiN Homepage

Objective 1
Objective 2
Objective 3

In this picture and in the one at the top of the page, what do you notice about the refracted part of the beam? Which colors are refracted the most and which the least ?

Recall what we learned in Submodule 1 about the index of refraction of a material: it is the ratio of the speed of light in a vacuum to the speed of light in a specific medium. This speed affects the wavelength, also. The wavelength decreases as the light enters the medium and then increases back to its original value when it leaves the medium.

Click here to read more about refraction, the index of refraction, and why prisms break white light into a spectrum.

How else can we manipulate light?

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Copyright &copy1995
Steve Beeson, Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287