Pasteur proposed in 1848 that the rotation of the polarization plane of the light in a dilute medium is generated by the symmetry properties of the molecules of the medium where the light propagates. Our objective is to show that Pasteur hypothesis was correct using the basic knowledge of electromagnetism and quantum mechanics of the undergraduate physics course. We present a brief review of the fundamental concepts of the electromagnetic theory necessary to understand the optical activity. Next, using the quantum mechanical perturbation theory and taking into account the molecular symmetries we calculate the optical activity of the medium. It will be shown that the theoretical predictions, which are in good agreement with the experimental results, give support to the Pasteur conjecture.
optical activity; molecular symmetries