Describe the observation of optical activity made by Louis Pasteur.

(N/A) Louis Pasteur laid the foundation of modern stereochemistry in $1848$.
$(i)$ He observed that crystals of certain compounds exist as mirror images.
$(ii)$ He demonstrated that aqueous solutions of equal concentration of these two types of crystals show equal but opposite optical rotation.
$(iii)$ He believed that the difference in optical activity is related to the three-dimensional arrangement (configuration) of atoms in the crystals.
Note: Configuration refers to the three-dimensional arrangement of atoms around the carbon atom.