What type of stereoisomer is shown by butan-2-ol and how can we prove it?

The answer is optical isomerism. Optical isomerism exists when a carbon has 4 different groups attached to it. In Butan-2-ol, the second carbon has a hydroxy group, ethyl group, a methyl group and a hydrogen attached. Furthermore, to test if this molecule is an optical isomer, we shine plane polarised monochromatic light, which will not rotate the light.