School of Physics Lecture Demonstration Manual

Ob-2 Matching Refractive Indices (Wool in Methyl Salycilate)

Published: Wednesday 15 March 2006 - Updated: Monday 28 March 2011


To demonstrate why you should not wear woollen clothes when swimming in a bath of methyl salycilate.



Click on pictures to enlarge.

Matching Refractive Index Right Side Down

Matching refractive Index Right Side Up

Matching Refractive Indices Diagram


Matching Refractive Index


A large cylindrical beaker is divided into two portions by a sieve of glass rods. The upper portion contains a wad of wool that appears opaque; the lower portion contains methyl salycilate. Wool on absorbing this chemical becomes transparent. If the beaker is now inverted allowing the chemical to saturate the wool an object previously hidden in the wool becomes visible.

Safety notes

Sharps safety 


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