Abstract

Measurements have been made of the spectral reflectivity of electrostatically deposited magnesium oxide smoke coating from thicknesses of 0.2 mm to 8.0 mm. The theory of the photometric sphere was used to determine the coefficient of reflection. A glass sphere was used to avoid the reflective effects of an opaque material and to determine the uniformity of the coating. It was found that at 8.0 mm thickness, light from a source placed inside the sphere could be visibly detected through the coating. For thick coatings, the reflectivity was in good agreement with that reported by Benford, Lloyd, and Schwartz. However, at the thinner coatings the results were in reasonable agreement with Middleton and Sanders’ results. The color inside the illuminated sphere depended upon the coating thickness, and changed from a bluish cast through green to ivory as the thickness increased.

© 1955 Optical Society of America

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References

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  1. J. S. Preston, Trans. Opt. Soc. (London) 31, 15 (1929–30).
    [CrossRef]
  2. Frank Benford, Gen. Elec. Rev. 23, 72 (1920).
  3. Benford, Lloyd, and Schwartz, J. Opt. Soc. Am. 38, 445 (1948).
    [CrossRef] [PubMed]
  4. W. E. K. Middleton and C. L. Sanders, J. Opt. Soc. Am. 41, 419 (1951).
    [CrossRef] [PubMed]
  5. A. H. Taylor, J. Opt. Soc. Am. 21, 776 (1931).
    [CrossRef]

1951 (1)

1948 (1)

1931 (1)

1920 (1)

Frank Benford, Gen. Elec. Rev. 23, 72 (1920).

Gen. Elec. Rev. (1)

Frank Benford, Gen. Elec. Rev. 23, 72 (1920).

J. Opt. Soc. Am. (3)

Trans. Opt. Soc. (London) (1)

J. S. Preston, Trans. Opt. Soc. (London) 31, 15 (1929–30).
[CrossRef]

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Figures (7)

Fig. 1
Fig. 1

The glass sphere used in this experiment.

Fig. 2
Fig. 2

Schematic diagram of the apparatus used in obtaining the coefficient of reflection.

Fig. 3
Fig. 3

Schematic diagram of the apparatus used in electrostatic deposition.

Fig. 4
Fig. 4

Cross-section view of the 8.0-mm coating.

Fig. 5
Fig. 5

Comparison of relative transmittance of the electrostatic-deposited and the direct-smoked coatings.

Fig. 6
Fig. 6

Coefficient of reflection versus wavelength for electrostatic-deposited MgO. Thickness as parameter. (T=1.0 m should read T=1.0 mm.)

Fig. 7
Fig. 7

Top three curves of Fig. 6.

Equations (5)

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K = I 1 - I 2 ( A 1 / S ) I 1 - ( A 2 / S ) I 2 ,
d K = [ I 1 - I 2 ( I 1 - A 2 S I 2 ) 2 ] I 2 S d A 2 .
d K = [ I 1 - I 2 ( I - A 2 S I 2 ) 2 ] I 2 r 2 R ( R 2 - r 2 ) 1 2 d r ,
d K = 0.019 d r .
d K = 0.00125 d R .