# Shimmering Lenses

In this activity, learners use Jell-O to explore lenses and different angles of light entry.

## Required Materials

• 3 packets of Jell-O (lighter colors and sugar-free varieties work best)
• Hot water (read package for amount)
• Bowl
• Spoon or whisk
• Baking pan (8" x 8")
• Refrigerator (clear a space for the pan)
• Table knife
• Cutting board
• Flashlight
• Black electrical tape

## Activity Directions

1. Mix 3 packets of Jell-O with the directed portion of hot water. Do not add cold water; you want stiff Jell-O. Stir until the powder is dissolved.
2. Pour the Jell-O into a baking pan.
3. Refrigerate the Jell-O overnight.
4. Loosen the Jell-O by soaking the bottom of the pan in warm water for 15 seconds and running a knife along the edge of the pan. Transfer the Jell-O to a cutting board.
5. Use the knife to cut the Jell-O into convex and concave lens shapes. Also, cut a long thin rectangle of Jell-O.
6. Place strips of black electrical tape across the lens of the flashlight to create a few narrow beams of light.
7. Turn your flashlight on and darken the room.
8. Shine the light through the Jell-O lenses and look at how light exits each lens.
9. Shine the light in either of the two shorter sides of the rectangle. Gently bend the rectangle. What happens to the light inside?
10. Try different angles of light entry into the lenses by moving the flashlight up and down each lens.
11. Try shining the flashlight with and without tape.
12. What is happening with the beams of light in the Jell-O? What happens with the rectangle? What happens if you bend the rectangle to the point that it begins to come apart?
Optional: Watch this video explaining how this activity works.

## Here's What's Happening

In a convex lens, the light rays converge (bend) together until they meet at a single point. They then crisscross and spread out again. In a concave lens, the light rays spread out never converging to a single spot. The strength of the lens depends on its shape and the material it is made of. If you have more Jell-O, try different curvatures and see how the light behaves with each shape. The neat thing about these simple lenses is that you can layer them to manipulate light in many ways. Optical engineers work with combinations of lenses every day to advance the technology of devices such as binoculars, microscopes and cameras.