Polarization refers to the orientation of Electric Field

Polarization refers to the orientation of Electric Field oscillations The m-waves are linearly polarized along the axis of the transmitter diode. The detector receives only the component of the incident m-wave parallel to the axis of the detector diode. When a linear polarizer is used, nearly all incident light is converted to linearly polarized light. Unfortunately, there is no way to detect to what extent light is actually polarized without a second polarizer (analyzer). We used the receiver for this.

Polarization When the analyzer’s transmission axis is aligned with that of the polarizer, the maximum intensity passes through. When the analyzer is rotated 90° to this, most of the light is absorbed and the minimum intensity is attained. When the receiver and transmitter are perpendicular, with a polarizer at angle q between them, the resulting intensity is detected as: I = I 0 cosq sinq which is a max for q = 45 degrees The percentage of polarized light (V) is then given by:

INCIDENT Polarization A Mechanical Analogy… ¶ Force pushes down on block ¶ Plane changes incident force’s direction by “absorbing” some of the incident force SM SO N D E RB Polarizer at 45 Degrees Receiver at 90 Degrees To Transmitter N A TR ED B R O B S A T EN D CI IN 3 IGNORED INCIDENT ED T IT 2 RECEIVED SM 1 AB I A TR ¶ Block moves parallel to plane’s “transmission axis” Initial Polarization Of Transmitted Wave D E TT

Polarization Resulting Intensity of Polarized light is given by Malus’ Law: Graph Malus’ Law: I(q) = I 0 cos 2 q The m-waves were found to be 98% polarized from the transmitter, but the wire polarizers, when used, were only 76% effective.

Polarization … via Rayleigh Scattering ¶ A wave packet incident on a small particle (<l/15) causes electron oscillations, creating a dipole. ¶ Light is re-emitted in a random direction, polarized parallel to the dipole oscillation axis. ¶ Incoming light undergoes the maximum polarization at 90° from the angle of incidence.

Polarization … via Rayleigh Scattering ¶ Atoms and molecules in the upper atmosphere are <1 nm in size, so they can scatter light in the visible spectrum (~400 nm<l<~700 nm) ¶ The intensity of the scattered light increases with (1/l)4, so the intensity of blue light scattered by the atmosphere is much greater than that of red light. ¶ Therefore, we have blue skies, red sunsets, and polarized light 90° from the sun.