Prisms Lab

Mr. Ahearn

2010

Introduction

A prism is a transparent optical element with flat, polished surfaces that refract light.

• Prisms are typically made out of glass, but can be made from any material that is transparent to the wavelength for which they are designed.

• A prism can be used to break light up into its spectral colors (ROY G BIV). Prisms can also be used to reflect light, or to split light into components.

HistoryLight changes speed as it moves from one medium to another

(for example, from air into the glass of the prism). This speed change causes the light to be refracted and to enter the new medium at a different angle.

In Newton’s time, it was believed that white light was colorless, and that the prism itself produced the color. Newton's experiments convinced him that all the colors already existed in the light.

Newton arrived at his conclusion by passing the red color from one prism through a second prism and found the color unchanged. From this, he concluded that the colors must already be present in the incoming light — thus, the prism did not create colors, but merely separated colors that are already there. He also used a lens and a second prism to recompose the spectrum back into white light.

Newton’s Experiment

Lab Question

What happens to visible light as it passes through a prism?

Goals

1. Construct a prism and observe the different colors that are produced

2. Infer how the bending of light waves depends on their wavelength.

Materials

• Microscope slides (3)

• Transparent tape

• Clay

• Flashlight

• Water

Procedure

1. Carefully tape the 3 slides together on their long sides so they form a long prism.

2. Place one end of the prism into a softened piece of clay so the prism is standing upright.

3. Fill the prism with water and put it on a table that is against a dark wall.

4. Shine a flashlight beam through the prism so the light becomes visible on the wall.

Conclude and Apply1. List the order of colors you saw on the wall2. Describe how the position of the colors on the wall

changes as you change the direction of the flashlight beam.

3. Describe how the order of colors on the wall changes as you change the direction of the flashlight beam.

4. Infer which color light waves have changed direction, or have been bent, the most after passing through the prism. Which color has been bent the least?

5. Infer how the bending of a light wave depends on its wavelength.

Now go write your report!

Works Cited

Ezrailson, Cathy, Nicholas Hainen, Deborah Lillie, and Dinah Zike. Waves, Sound, and Light.

New York: Glencoe/McGraw-Hill, 2008

"Prism (optics)." Wikipedia, the Free Encyclopedia. Web. 18 Nov. 2010. <http://en.wikipedia.org/wiki/Prism_(optics)>.