The Astrophysical journal . n I*-=.001, or density of vapor five times that in the case representedby Fig. I. Figs. 3 and 4 represent the ratioof intensities of transmitted to normallyincident light for the densities correspond-ing to Figs. I and 2 ; and Fig. 5 representsthe ratio for the density corresponding tothe value vi = .003. The following tablegives the breadths of the dark bands fordensities of vapor corresponding to valuesof m from .0002 to fifteen times that value ; and Fig. 6 represents graphically the breadths of the dark bandsand their positions relatively to the bright lines D^,
The Astrophysical journal . n I*-=.001, or density of vapor five times that in the case representedby Fig. I. Figs. 3 and 4 represent the ratioof intensities of transmitted to normallyincident light for the densities correspond-ing to Figs. I and 2 ; and Fig. 5 representsthe ratio for the density corresponding tothe value vi = .003. The following tablegives the breadths of the dark bands fordensities of vapor corresponding to valuesof m from .0002 to fifteen times that value ; and Fig. 6 represents graphically the breadths of the dark bandsand their positions relatively to the bright lines D^, Dg for thefirst five values of ni in the table. Fig. 6. vtii/fi ,f n. Breadths of bands D, Dj . .0010 . . 09 217 293 371392408419 .11 • 7. According to Sellmeiers formula the light transmittedthrough a layer of sodium-vapor (or any transparent substance 2 35 LORD KELVIN to which the formula is applicable) is the same whatever be thethickness of the layer (provided of course that the thickness isat least several wave-lengths, and that the ordinary theory of thetransmission of light through thin plates is taken into accountwhen necessary). Thus the D,, Dg lines of the spectrum ofsolar light, which has traveled from the source through a hun-dred kilometers of sodium-vapor in the Suns atmosphere, mustbe identical in breadth and penumbras with those seen in a lab-oratory experiment in the spectrum of light transmitted throughhalf a centimeter or a few centimeters of sodium-vapor, of thesame density as the densest part of the sodium-vapor in the por-tion of the solar atmosphere traversed by the
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectspectru, bookyear1895
