Refraction with Water and Glass
Introduction:
Galileo’s telescope revolutionized the way we observe the heavens. One of the key principles behind its function is refraction, the bending of light as it passes through different materials. This experiment introduces children to the basic physics of light, helping them understand how Galileo used lenses to magnify distant objects in the sky. By playing with glass, water, and light, young learners can observe how the direction and focus of light changes — the same concept Galileo relied on to study the moon, Jupiter, and beyond. This activity links the physics of optics with the practical design of scientific tools. It also emphasizes how something invisible like a light beam can become visible when we explore it through hands-on observation.
What You Will Need:
A clear drinking glass
Water
A pencil or straw
White paper
A flashlight (optional for low-light rooms)
Notebook and pencil for observations
Step-by-Step Instructions:
Fill the glass about three-quarters full with water.
Place the pencil or straw in the glass.
Look at the pencil from the side of the glass. Does it appear straight or bent? Try observing from different angles.
Now remove the pencil and hold it behind the glass, without water. Look through the glass again.
Slowly pour the water into the glass while watching the pencil through the water. Observe how the pencil seems to shift or break.
If indoors, dim the lights and shine a flashlight through the side of the glass. Watch how the light bends and changes direction inside the water.
Place a white piece of paper behind the glass and notice any light distortions or changes in the pencil’s appearance.
What to Look For:
What happens to the pencil or straw when it is viewed through the water?
How does the shape of the glass affect the image?
Does the light path change when you move your eyes or the flashlight?
Fun Fact:
Galileo did not invent the telescope, but he was the first to improve it for space observation. His use of convex and concave lenses magnified the night sky up to 30 times — enough to see the craters on the moon and Jupiter’s moons!
Safety Tip:
Avoid using glass containers around small children without supervision. If using a flashlight, do not shine it directly into eyes.
Journaling Prompt:
Draw what the pencil looks like before and after adding water. Why do you think it appears broken or bent? Write a sentence about what this might mean for how a telescope helps us see things more clearly and from far away.
