When a plane-polarized light is passed through one of the 2 enantiomers of a chiral molecule that molecule rotates light in a certain direction. ... Because chiral molecules are able to rotate the plane of polarization differently by interacting with the electric field differently, they are said to be optically active.

Are chiral molecules optically active?

Not only chiral molecules are optically active. Optically active means they rotate the plane of polarization.

Why do chiral molecules rotate polarized light?

Optical activity describes the phenomenon by which chiral molecules are observed to rotate polarized light in either a clockwise or counterclockwise direction. This rotation is a result of the properties inherent in the interaction between light and the individual molecules through which it passes.