Question

Why does specific rotation of plane-polarized light INCREASE with increased concentrations of the stereoisomer?

Answer 1

Because specific rotation is determined by concentration........

Explanation:

It has been a long time since I had to use a polarimeter, however, a cell of FIXED path length is filled with a KNOWN concentration of solution containing the analyte. The degree of optical rotation, `alpha`, depends on the path length of the cell, and also on the concentration of solution contained in the cell. Of course this is consistent with the fundamental principles of all spectroscopy: signal depends on the path length, and on the concentration of absorbing species within that path length.