Abstract

A polarizing prism properly oriented was found to darken the sea relative to the sky, to reduce the brilliance of the sun path and to render the horizon more distinct. In bright weather it increased the visibility of objects against the sea background. Attaching polarizing prisms to a sextant and to binoculars improved these instruments in certain cases. Measurements of the light of the sea ruffled by a breeze from several hundred yards from the observer out to the horizon several miles away showed that the light was often more, and rarely less, than 2/3 polarized with electric vector mainly horizontal but tilted up under certain conditions, e.g., tilted up 30° for the sun bearing 90° and at 45° altitude. From the observations and theory it came out that the sea light was the light of the sky at about 25° to 35° above the horizon reflected by the sea, the reflecting facets of the sea surface being most frequently at about 15° to the horizontal. The width of the sun path calculated from this was in agreement with the observed width of about 6°, 14° and 18° in moderate weather for the sun at altitudes 10°, 20° and 30°, respectively. The explanation is given of a number of breezy sea reflection phenomena.

© 1934 Optical Society of America

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References

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  1. Raman, The Molecular Scattering of Light, The University of Calcutta Press (1922); W. Smosarski, Gerlands. Beitr. z. Geophysik 38, 97 (1933); and references infra.
  2. Stokes, Mathematical and Physical Papers 1, 227 (1880).

1880 (1)

Stokes, Mathematical and Physical Papers 1, 227 (1880).

Raman,

Raman, The Molecular Scattering of Light, The University of Calcutta Press (1922); W. Smosarski, Gerlands. Beitr. z. Geophysik 38, 97 (1933); and references infra.

Stokes,

Stokes, Mathematical and Physical Papers 1, 227 (1880).

Mathematical and Physical Papers (1)

Stokes, Mathematical and Physical Papers 1, 227 (1880).

Other (1)

Raman, The Molecular Scattering of Light, The University of Calcutta Press (1922); W. Smosarski, Gerlands. Beitr. z. Geophysik 38, 97 (1933); and references infra.

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Figures (6)

Fig. 1
Fig. 1

a, b, c, unpolarized and a′, b′, c′, polarized photographs of sun path. a, a′, Atlantic Ocean, altitude of sun 48°, bright blue scene, breeze 12 knots, sea smooth; b, b′, Chesapeake Bay, altitude of sun 39°, bright blue scene, breeze 18 knots, bay choppy; c, c′, Long Island Sound, altitude of sun 26°, hazy, blue gray scene, breeze 6 knots, sound smooth.

Fig. 2
Fig. 2

Polarization of sun path; curve, theoretical, and dots, experimental.

Fig. 3
Fig. 3

Polarizing binoculars.

Fig. 4
Fig. 4

Polarization photometer.

Fig. 5
Fig. 5

Sun path. α=7°, 13°, 20°, 30°, w=3°, 7°, 14°, 18° and breeze 3, 10, 18, 18 knots for a, b, c, d, respectively.

Fig. 6
Fig. 6

Width of sun path; curves, theoretical, and dots, experimental.

Tables (1)

Tables Icon

Table I Altitude of sun 45°.

Equations (9)

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ρ 1 = [ - sin ( i - r ) / sin ( i + r ) ] 2 ,
ρ 2 = [ - tan ( i - r ) / tan ( i + r ) ] 2 ,
sin i = μ sin r ,
R = ( ρ 1 + ρ 2 ) / 2.
tan φ = ( ρ 2 / ρ 1 ) 1 2 .
γ = ρ 2 / ρ 1 .
δ = α / 2 ,
α = 2 ( 90 ° - i ) .
w = f ( α , δ ) .