File:Selective radiation from various solids (1908) (14747163706).jpg

Identifier: select515919119089797unse (find matches)
Title: Selective radiation from various solids
Year: 1908 (1900s)
Authors:
Subjects: rays and radiation light reflection spectra
Publisher: National Bureau of Standards
Contributing Library: NIST Research Library
Digitizing Sponsor: NIST Research Library

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ytoward the short wave-lengths, being at about i.8/x for an energyconsumption of 13.6 watts. The pure oxide is not an efficientradiator of white light, and only becomes so when a small amountof cerium, thorium, or yttrium oxide is added, which combinationis the Nernst glower previously investigated.^ In addition to the sharp emission lines at 2.8 and 4.35/>t, thereare wide hazy bands at 2 and 2.4ft (appears on curve d), while from5 to 6fjL there is a wide band which is evidently unresolved, themaximum shifting toward the short wave-lengths with rise intemperature. The extraordinary rapidity which characterizes thegrowth of the emissivity at 1.5 to 2/jl is worthy of notice. In onecase where the ratio of emissivities at 4.3/x, for a given increase inenergy, is 50, it is almost 200 at 2/1. 2. Oligodasel^I^^^^^^^^J^A 9 x 2.8 mm. Energy ^This Bulletin, Vol. 4, p. 533; 1908. ^ Transmission curves. Carnegie Publication No. 65, p. 64. Coblentz.) Selective Radiation from Various Solids. 165
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4 5 WAVE LENGTH 166 Bulletin of the Bureau of Standards. \voi.5,no.2. supplied was 8.6 watts and 13.3 watts. Curves a and h, Fig. 3.)The original crystal, as well as the glass rod, were perfectly trans-parent. The rod showed no color on suddenly throwing off thecurrent. The platinum terminals melted on 16 watts, but the rodshowed no color. As in the preceding feldspars there are bandsat 2, 2.88, 3.1, 4.1, 4.5, and 7/>t. The absorption band at 4.8/xseems to be shifted to 4.5/>t in the emission spectrum. Curve cgives the emissivity of a rod 2.5 cm long, 2.1 mm diameter, heated(on 29.4 watts) until it became viscous (temperature about 1200°C), but did not sag. The radiation was taken from a length of5 mm of the central portion of the filament by shielding it. Thecurve is conspicuous in showing that at 2/Lt the intensity hasincreased but little as compared with the band at 2.9/-t. Theisochromatics of this filament are given in Fig. 14. In curves aand h the ends of the rod were not

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