Children can best understand what causes rainbows by exploring how refraction bends light. These experiments demonstrate refraction, including the bending of white light to create a spectrum.

To demonstrate refraction of light

You will need materials for groups of two or three students.

• clear glasses with straight sides
• craft sticks
• flashlights
• cardboard
• white cardstock (8 1/2 in. by 11 in.)
• prisms (optional)
• drawing paper
• markers or crayons

1. Before the lesson, prepare the flashlights. Unscrew the flashlights and take out the plastic lenses. Trace a circle on cardboard the same size as the lens. The cardboard should be opaque so light does not filter through. Cut the circle out and then cut it in half. Trim a thin slice off each flat side of the semicircles. Place the circle halves over the lens. Adjust the pieces so there is a thin space in the center of the lens. Screw the flashlights back together. (If the cardboard is too thick to completely close the flashlights, you can tape the cardboard pieces on the outside of the lens.)
   
2. Give each group a glass of water and a craft stick. Ask students to look at the stick in and out of the water. Have them make observations about what they notice. Encourage them to hold the stick at different positions and look at it from different angles. Talk about how the water refracts (bends) the light to make the stick look bent.
   
3. Explain that if light is refracted, a spectrum (rainbow) appears. Challenge students to use the flashlights to make a spectrum on the white cardstock. It helps to darken the room. Hint that they should place the glass of water near the edge of the table and hold the white cardstock below the glass. Have them experiment with the angle and direction of the light shaft. Ask: What colors do you see? What colors are next to each other?Explain how the glass of water refracts the light like water drops do to create a rainbow.
   
4. Have students draw a rainbow and color in the bands with the colors they observed.
   

1. How did refraction change the way the craft stick looked?
   
2. What causes light to bend?
   
3. How do you know white light is made of different colors?
   
4. What colors do we see in a rainbow?
   
5. How is the spectrum you made like a rainbow in the sky?
   

1. Use prisms and white cardstock outdoors to create rainbows. Have students experiment with the angle of the prism and the position of the cardstock. Ask them to explain the best way to refract sunlight with a prism. Ask them to compare the prism-created spectrum with the ones formed by using the glass of water.
   
2. Make a rainbow window in your classroom. Place different sized clear bottles and plastic containers of water near the window. Hang crystals and pieces of smooth glass or plastic in front of the window. Encourage students to make observations about light refracting through these materials.
   
3. Fill a rectangular aquarium with water. Place a container of pennies, a plastic ruler, and other small objects by the aquarium. Keep several flashlights with the cardboard slit lens nearby. Encourage children to explore refraction by using these materials. This setup makes a great discovery station. It is amazing how much students can observe and discover with this simple arrangement.