A simple, low-cost, fully automated polarimeter, which demonstrates fundamental properties of skylight scattering and polarization for undergraduate physics students, is described. The polarimeter includes a microprocessor-based control unit, a Sun tracker, an elevation-azimuth mount with two degrees of freedom, and a polarization sensor unit equipped with a light-dependent resistor for measuring light intensity. Results obtained in the principal plane of the Sun using the polarimeter on a relatively clear day, together with the theoretically expected results for a molecular atmosphere, are presented. A root-mean-square error comparison indicates fairly good agreement between theory and experiment. Construction and experimentation with the polarimeter will provide students with insight into important physical concepts involved in skylight scattering and polarization as well as improve their instrumentation capabilities.
References
1.
Frank L.
Pedrotti
and Leno S.
Pedrotti
, Introduction to Optics
, 2nd ed. (Prentice Hall
, Englewood Cliffs, NJ
, 1993
), pp. 298
–306
.2.
G. P.
Konnen
, Polarized Light in Nature
(Cambridge U. P.
, Cambridge
, 1985
), pp. 19
, 30, and 37.3.
Glenn S.
Smith
, “The polarization of skylight: An example from nature
,” Am. J. Phys.
75
, 25
–35
(2007
).4.
Ramon
Hegedus
, Susanne
Akesson
, and Gabor
Horvath
, “Anomolous celestial polarization caused by forest fire smoke: Why do some insects become visually disoriented under smoky skies?
,” Appl. Opt.
46
, 2717
–2726
(2007
).5.
Gabor
Horvath
, Jozsef
Gal
, and Istvan
Pomozi
, “Polarization portrait of the Arago point: Video-polarimetric imaging of the neutral points of skylight polarization
,” Naturwissenschaften
85
, 333
–339
(1998
).6.
K. L.
Coulson
et al., Polarization and Intensity of Light in the Atmosphere
(A. Deepak Publishing
, Hampton, VA
, 1988
), pp. 4
, 179, and 551.7.
G. S.
Isaev
, “Some results of photoelectric measurements of atmospheric polarization in the town of Shakhty
,” in Atmospheric Optics
, edited by N. B.
Divari
(Consultants Bureau
, NY
, 1970
), pp. 86
–89
.8.
D. G.
Stamov
, “Light polarization as an independent measure of atmospheric purity and transmittance
,” in Atmospheric Optics
, edited by N. B.
Divari
(Consultants Bureau
, NY
, 1970
), pp. 80
–85
.9.
K. L.
Coulson
et al., “Photon-counting polarizing radiometer
,” Appl. Opt.
13
, 497
–498
(1974
).10.
George G.
Holzworth
and C. R.
Nagaraja Rao
, “Studies of skylight polarization
,” JOSA
55
, 403
–408
(1965
).11.
Jacqueline
Lenoble
, “Scattering and polarization of the solar radiation in the Earth's atmosphere. Historical review and present applications
,” Citation: AIP Conf. Proc.
1100
, 7
(2009
).12.
D. J.
Gambling
and B.
Billard
, “A study of the polarization of skylight
,” Aust. J. Phys.
20
, 675
–681
(1967
).13.
Kenneth J.
Voss
and Yi
Liu
, “Polarization radiance distribution measurements of skylight. I. System description and characterization
,” Appl. Opt.
36
, 6083
–6094
(1997
).14.
“PIC16F887 Data sheet,” <http://www.microchip.com>.
15.
“4 × 20 LCD Data sheet,” <http://www.hwkitchen.com/products/lcd-display-4x20-characters>.
16.
“LM 324 Data sheet,” <http://www.ti.com/product/lm324>.
17.
“LM 298 Data sheet,” <http://www.alldatasheet.com/view.jsp?Searchword=L29820datasheet>.
18.
“L297 Data sheet,” <http://www.alldatasheet.com/view.jsp?Searchword=L29720datasheet>.
19.
Giorgos
Lazaridis
, “How Stepper Motors Work
,” 7 May 2010
, <http://www.pcbheaven.com/wikipages/How_Stepper_Motors_Work>.20.
C. P.
Abayaratne
et al., “A low cost partially automated polarimeter for investigating skylight polarization
,” J. Natl. Sci. Found. Sri Lanka
44
, 95
–103
(2016
).21.
Nathan J.
Pust
and Joseph A.
Shaw
, “Comparison of skylight polarization measurements and MODTRAN-P calculations
,” J. Appl. Remote Sens
, 5
, 053529-1
–053529-16
(2011
).22.
Eyk
Boesche
, Piet
Stammes
, Thomas
Ruhtz
, Rne
Preusker
, and Juergen
Fischer
, “Effect of aerosol microphysical properties on polarization of skylight: Sensitivity study and measurements
,” Apl. Opt.
45
, 8790
–8805
(2006
).23.
Josef
Gal
et al., “Polarization patterns of the summer sky and its neutral points measured by full-sky imaging polarimetry in Finnish Lapland north of the Arctic Circle
,” Proc. R. Soc. London, A
457
, 1385
–1399
(2001
).24.
Nathan J.
Pust
and Joseph A.
Shaw
, “Wavelength dependence of the degree of polarization in cloud-free skies: Simulations of real environments
,” Opt. Express
20
, 15559
–15568
(2012
).25.
Josef
Gal
et al., “Polarization of the moonlit clear night sky measured by full-sky imaging polarimetry at full Moon: Comparison of the polarization of moonlit and sunlit skies
,” J. Geophys. Res.
106
, 22647
–22653
, doi: (2001
).© 2017 American Association of Physics Teachers.
2017
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