Advanced Laboratory and/or Demonstration Apparatus

Apparatus Title: Polarization of reflected light

Abstract : The apparatus consists of a ray box, an acrylic prism, a glass slide, and a polarizing sheet. The apparatus can demonstrate polarization of reflected light at the Brewster angle and variation of the level of polarization with angle of incidence.

Description Polarization of Reflected Light

A ray box that gives parallel rays of light from one end and a diverging beam from the other end is used in this apparaus. As shown in Fig.1 an acrylic prism is placed in the parallel rays symmetrically. The angle of incidence of the rays falling on the prism is 600, very close to the Brewster angle of acrylic (57.50), and, therefore, the reflected rays are almost completely polarized. The polarization can be demonstrated by placing the polarizer in front of the ray box and changing its orientation. When the polarizer is held horizontally the reflected light disappears showing that the reflected light is polarized in the perpendicular direction (Fig.1).

Angular dependence of polarization of reflected light can be demonstrated with the help of the diverging rays. A glass reflector (microscope slide) is placed so that the angle of incidence of the rays falling on the glass is lower than, equal to, and higher than the Brewster angle. When the polarizer is held horizontally the fourth ray of light disappears (Fig.3) because the angle of incidence is equal to Brewster angle. The other rays with angles of incidence less than and greater than Brewster angle are visible because they are not completely polarized.

Conclusions

This is the cheapest, easiest, and quickest way of demonstrating the different aspects of polarization of reflected light.