Sulfur Dioxide


Sulphur dioxide is upright. See video below.
The apparatus. When viewed through the lens, SULPHUR seems to be inverted while DIOXIDE seems to be upright. See photo and video below.

A cylindrical lens appears to invert the word SULPHUR but not DIOXIDE.


Both sulfur and sulphur are accepted these days, but sulfur is now preferred in most places.

Note the demonstration works well with CARBON DIOXIDE as well.



Principles Illustrated

Really just fun, but it does help to illustrate the concept of symmetry and also helps develop critical thinking and problem solving skills.

NCEA & Science Curriculum

SCI 1.3, PHYS 1.4, PHYS 2.3


It appears sulphur is inverted but dioxide is not. Is this true?
It appears sulphur is inverted but dioxide is not. Is this true?

Ask students why SULPHUR is inverted but dioxide is not. Suggest dispersion (ask what prism does). Try to convince them that the cylindrical lens inverts the blue word but not the red word because the refractive index of the magic liquid (water) is larger for blue. Then admit it’s all untrue and show that DIOXIDE looks the same if flipped. You can prove the point by adding a small bit of Blu-Tack to the top of one of the letters in DIOXIDE and it will appear at the bottom when viewed through the lens.

This can be done with a Perspex or glass rod. This version which is about a meter long, is suitable for a somewhat larger class.

VIDEO: SuphurDioxide.mp4


Individual teachers are responsible for safety in their own classes. Even familiar demonstrations should be practised and safety-checked by individual teachers before they are used in a classroom.

Related Resources

Teaching Resources

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This teaching resource was developed with support from

The MacDiarmid Institute
Faculty of Science, Victoria University of Wellington
School of Chemical and Physical Sciences, Victoria University of Wellington


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