2
$\begingroup$

By Malus' law we know that when an unpolarised light falls on a thin glass sheet, the light that gets reflected is polarised light as only the s-component (only 15%) is present with very low intensity while the refracted light is a mixture of s-component or p-component with high intensity.

s- component being the perpendicular component p-component being the parallel component

Can someone explain the below mentioned reasoning for the reflected light to contain no parallel component of light?

The physical mechanism for this can be qualitatively understood from the manner in which electric dipoles in the media respond to p-polarized light. One can imagine that light incident on the surface is absorbed, and then re-radiated by oscillating electric dipoles at the interface between the two media. The polarization of freely propagating light is always perpendicular to the direction in which the light is travelling. The dipoles that produce the transmitted (refracted) light oscillate in the polarization direction of that light. These same oscillating dipoles also generate the reflected light. However, dipoles do not radiate any energy in the direction of the dipole moment. If the refracted light is p-polarized and propagates exactly perpendicular to the direction in which the light is predicted to be specularly reflected, the dipoles point along the specular reflection direction and therefore no light can be reflected.

$\endgroup$
  • 1
    $\begingroup$ This won't answer things fully, but should help you find some more things to read: en.wikipedia.org/wiki/Brewster's_angle $\endgroup$ – tmwilson26 Feb 3 '16 at 14:10
  • $\begingroup$ "why" is misleading, in that we really say "here's a set of equations which appear correctly to model the observed behavior." $\endgroup$ – Carl Witthoft Feb 3 '16 at 15:04
  • $\begingroup$ @Carl Witthoft Whilst I entirely agree with you I fear that you are losing the battle if not the war. As you quite rightly explained the word "why" should be replaced by a more meaningful word or phrase but just a glanced at the posts in this forum will show that the easier option of writing the short word "why" is favoured. $\endgroup$ – Farcher Feb 3 '16 at 15:11
  • 1
    $\begingroup$ @tmwilson26 Thanks for the link however I am unable to understand what was written in the mentioned qualitative analysis.. $\endgroup$ – S_Learner Feb 3 '16 at 15:26