Optical activity from extra dimensions

Optical activity, like the Faraday effect, is a rotation of the plane of polarization of propagating light in a medium and can be attributed to different sources with distinct signatures. In this Rapid Communication we discuss the effect of optical activity in vacuum due to the Kaluza-Klein scalar field $\phi ,$ in the presence of an external electromagnetic field. The astrophysical implication of this effect is indicated. We also point out the possibility of observing the same in laboratory conditions.