Experiment with bending light
Seeing isn’t always believing – especially when refraction is involved. Bend a pencil or make a glass disappear with these simple experiments.
Light travels through different materials at different speeds. When light travels from one material to another it changes speed, causing it to bend.
Want to see it for yourself?
Materials
- Pyrex glass containers (one large and a smaller one that fits easily inside)
- Vegetable oil
- Water
- Pencil
Steps
1. Place the pencil into a glass of water so that only one end is in the water. Look at the pencil from the side, what do you see? It might look like your pencil is broken or split.
When you look at the pencil, you're viewing part of it through air and part through water. Light travels through these materials at different speeds. The change in speed causes the light to bend, or refract. Because of this the part of the pencil that is in water appears shifted.
Now let’s try a second experiment – but be careful, this one's going to be messy!
1. Place the small pyrex container into the larger container full of water. What do you see?
2. This time, fill the large container with vegetable oil. Place the small pyrex glass container into the large container full of oil, but don’t let any oil get inside.
So far, everything should look pretty normal.
3. Finally, submerge the small container so that it fills up with oil.
Look closely. It disappears before your eyes!
Pyrex glass and vegetable oil bend light the exact same amount, so one appears invisible inside the other. Because the light isn't refracted or reflected you have no way to see the inner glass.