A clear blue sky viewed through a linear polarizer. (a) The polarizer is oriented for maximum transmission (transmission axis, white arrow, is normal to the principal plane). (b) The polarizer is oriented for minimum transmission (transmission axis is parallel to the principal plane). From the light meter readings that go with these photographs, the degree of linear polarization is .
Schematic drawing of the observation of the polarization of skylight in the principal plane (the plane containing the points S, P, and M).
The action of an ideal linear polarizer on waves with various states of polarization: (a) linearly polarized light, (b) natural light, and (c) partially polarized light composed of linearly polarized light plus natural light.
Details for the scattering of natural light by an electrically small element in the atmosphere. The points S, P, and M lie in the principal plane, and the unit vectors and are normal to this plane. The inset shows the radiation patterns in the principal plane for the two components of the electric dipole moment: , which is normal to the principal plane, and , which is in the principal plane.
Degree of linear polarization for light from the zenith sky versus the angle of elevation of the sun, . The measured data are from 1947 (Ref. 16) and from 1977 (Ref. 2).
(a) Drawing of the principal plane showing the unit vectors and pointing from the observer toward the sun and toward the observation point, respectively. (b) Construction for a circle on which the degree of linear polarization is a constant.
Polarization diagram for the entire sky when . The length of the heavy line indicates the degree of linear polarization ; the line is parallel to the direction of the linearly polarized component of the electric field. Results are shown for two orientations: (a) mainly the solar half of the sky and (b) mainly the anti-solar half of the sky.
Contour plots for the degree of linear polarization for . (a) Simple theory. (b) Measured data at (Refs. 18 and 19). The position of the sun is shown by the small symbol.
Schematic drawings showing von Frisch’s experiment demonstrating the honey bee’s orientation by polarized light. Each figure shows the bee’s tail-wagging dance on a horizontal comb of the hive. (a) During the dance, the sun is visible to the bee. (b) During the dance, a patch of clear blue sky is visible to the bee, and the view of the sun is blocked (indicated by gray area). (c) Same as in (b) with the skylight passing through a linear polarizer, and the transmission axis of the polarizer aligned with the linearly polarized component of the electric field of the skylight. (d) Same as in (c) with the transmission axis of the linear polarizer rotated.
Elements in the bee’s detection of polarized light. (a) The compound eye of the worker bee composed of about 5000 ommatidia. The inset shows the ends of the ommatidia visible on the surface of the eye. The specialized ommatidia involved in the detection of polarized light are in the dorsal rim area, which is shown in black. (b) Longitudinal and transverse cross sections for one of the specialized ommatidia composed of nine visual cells (Refs. 25 and 29). (c) A single visual cell from (b), showing the details for the microvilli (Ref. 37). (d) An expanded view of the transverse cross section of the ommatidium in (b) showing the three UV sensitive visual cells (A, B, and C) in gray, and the orthogonal orientation of the microvilli in the rhabdom (Ref. 25).
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