This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1903 Excerpt: ...of the spectrum of one light compared with another light without regard to the total intensity of either light. Thus we may choose any light as a standard of comparison, say gaslight. In comparing another given light with this, we may make the other light of such intensity as to reduce the two spectra to equal ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1903 Excerpt: ...of the spectrum of one light compared with another light without regard to the total intensity of either light. Thus we may choose any light as a standard of comparison, say gaslight. In comparing another given light with this, we may make the other light of such intensity as to reduce the two spectra to equal intensity in the region of the D line. Then we may express the intensity of any other part of the spectrum of the given light in terms of the intensity of the corresponding part of the spectrum of gaslight. The curves in Fig. 142 show the results of a spectropho tometric comparison of daylight and limelight with gaslight. The composition of the gaslight is represented by a horizontal straight line, inasmuch as the intensity at each part of the spectrum of gaslight is taken as the unit intensity for that part of the spectrum. The daylight and limelight are each of such total intensity as to have the same intensity as the gaslight in the region of the D line (wave-length 0.59//). The ordinate of the daylight (or limelight) curve at any point represents the number of times brighter the daylight (or limelight) spectrum is than the gaslight spectrum at that point. Thus, daylight, which has the same intensity as gaslight at the D line, is only about-fa as bright as the gaslight at wave-length 7,000, and more than twenty times as bright as gaslight at wavelength 4,500. The curves in Figs. 143 and 144 show the results of a spectrophotometric study of gaslight which has passed through a solution of potassium chromate, and of gaslight which has been reflected from powdered ultramarine blue, both referred to gaslight direct. The ordinates in Fig. 143 show the fractional parts of the various wave-lengths of gaslight which are transmitted by the solution and the o...
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