Fill several different sizes and shapes of clear drinking glasses with water in varying amounts. For example, fill a large ice tea glass halfway, a small shot glass all the way to the top and a juice glass about 3/4 full. The important part is to gather as many different sizes and shapes of glasses as you can.

Place the glasses on a flat surface such as a coffee table. Push the glasses slightly over the edge of the table, so that slightly less than half of the glass bottom is hanging over the edge of the table.

Place the large white bedsheet on the floor in front of the glass. This will serve as your "screen" for being able to see the colored spectrum clearly as the light shines through each glass and creates a rainbow.

Switch on the flashlight and shine the light from behind the glasses, toward the sheet. You may need more than one flashlight for this step, especially if you are using a number of different glasses. You may have to experiment with the angle of the light in order to create a clear rainbow spectrum on the white sheet, perhaps even standing on a chair or stepladder to create the right effect.

Create ripples in the water with your fingers to make your rainbows appear to sparkle and shimmer.

Place the glasses of water in a sunny window for the same effect. Experiment with where you place the sheet in order to see your rainbows clearly. Compare and contrast the different sized rainbows you have created with the different glasses. Some glasses and water amounts may produce two rainbows.

Use a baster to take water away from some glasses and add water to others in order to change the effect of the rainbow on the sheet. Ask children open-ended questions about the rainbows to help them understand how their homemade prisms break the light into hues of red, orange, yellow, green, blue, indigo and violet.