6A40.30 Disappearing Glass Tubes
Refractive index, refraction, geometrical optics
Light refracts and reflects when it reaches a medium with a different index of refraction. The index of refraction of mineral oil is almost identical to that of a glass tube, so light does not refract or reflect between the oil and glass, making the glass almost invisible in oil.
-  Beaker
-  Glass tube
-  Water bottle
-  Bottle of mineral oil
-  Document camera or overhead projector
- Place the beakers, each with a glass tube inside, as desired for an overhead projector or document camera.
- Put the bottles of water and mineral oil nearby.
- After the demo, please return the mineral oil to its container for re-use!
- Pour water into the beaker for water. Note how the tube is visible due to refraction and reflection at the interface.
- Pour mineral oil into the other beaker. The submerged section of tube should almost disappear.
- PIRA 6A40.30
- Don't attempt this at home!
If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.