How to bend light by creating a prism with a glass of water

By: Molly Duffy Feb. 22, 2021 1:47 pm Updated: Feb. 22, 2021 1:48 pm

Although our eyes usually can't see them, visible light contains all the colors of the rainbow.

This kind of light is called 'white light,' and it's the light we get from the sun, a lamp or a flashlight. Inside white light are the colors of the rainbow: red, orange, yellow, green, blue, indigo and violet.

To see those colors, you need something called a prism — an object that can refract light and break it up, according to Sciencing, by the color's wavelengths.

Prisms work, in part, because colors travel at different speeds from each other. Red is the fastest, according to the University of Wisconsin-Madison, which is why red is always at the top of a rainbow. Violet is the slowest, which puts it at the bottom. All the other colors travel at speeds somewhere in between.

A simple way to fracture white light into a rainbow is by creating a prism with a glass of water. From Sciencing, here's how.

What you'll need:

•

A drinking glass

•

Flashlight

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One or two pieces of white paper

1. Fill a glass about halfway full with water, and place it on the edge of a table. It should hang a little over the edge, but be careful not to spill! Place a couple white pieces of paper on the floor below the cup.

2. Shine a flashlight through the glass. Try out a few different angles and see what works best to create the image of a rainbow onto the papers.

3. Examine the rainbow you create. Did your light fracture into one rainbow, or into several? Can you see all seven colors in your rainbow?

Comments: molly.duffy@thegazette.com

2. Shine a flashlight through the glass. Try out a few different angles and see what works best to create the image of a rainbow onto the papers.

3. Examine the rainbow you create. Did your light fracture into one rainbow, or into several? Can you see all seven colors in your rainbow? (Molly Duffy/For The Gazette)