Can Water Bend a Straw Video
Supplies Needed
- Empty Glass
- Water
- Plastic Straw
Experiment Instructions
Step 1 – Observe the straw and notice that it is perfectly straight. Next, place the straw in the empty glass and take note that the straw is still straight.
Helpful tip: Use a large plastic straw from a water bottle to see the results more clearly.
Step 2 – Pour water into the glass until it is nearly full. Look directly at the side of the glass at the straw. What do you see?
Step 3 – You will notice that near the top of the water line the straw appears to bent. Remove the straw from the water. Is it still bent?
How Does the Experiment Work?
When you add the water to the glass, the straw appears to bend, but once you remove the straw you see it isn’t really bent at all. This is because the straw is not bending, but the light around the straw is bending due to refraction. Light refracts as it passes from one medium to the next because it travels at different speeds through those mediums. Light travels fastest through air, a little slower through water, and even slower through glass.
Refraction is the bending of light as it passes from one medium into another (ie. air to water, water to air).
We need light in order to see. When we look at the straw outside of the glass of water, the light coming from the straw travels through the air straight to your eye. As you look at the straw in the glass of water, the light coming from the straw to your eye bends as it passes through three different mediums (water, glass, and air). As the light passes from one medium to the next, it changes speed and bends.
How Does the Experiment Work?
Try this experiment with liquids other than water. Liquids to try would be light corn syrup, rubbing alcohol, or clear Gatorade. Does the liquid you use affect how much the straw appears to bend?
I hope you enjoyed the experiment. Here are some printable instructions:
Can Water Bend a Straw Experiment
Materials
Instructions
Optical illusion