Each spectral component of a polarized polychromatic beam suffers a change in its state of polarization during its propagation through a birefringent plate. The change in the polarization state depends on the wavelength of light because the retardation introduced between two orthogonal components varies inversely with wavelength. This implies that the passage of a polarized polychromatic beam will induce a 'polarization dispersion' of different spectral components. Thus, the beam coming out of the birefringent plate will behave as a partially polarized light even if the incident beam is fully polarized. In the present communication, we study the phenomenon of depolarization of a polarized polychromatic beam having a flat top spectral profile during its propagation through a linear birefringent medium. © 2016 Elsevier GmbH. All rights reserved.