Photo-chemistry / by S.E. Sheppard.

  • Samuel Edward Sheppard
Date:
1914
Catalogue details

Licence: In copyright

Credit: Photo-chemistry / by S.E. Sheppard. Source: Wellcome Collection.

    74/484 page 58
    radiation of the two. The results obtained, using a surface bolometer, are given in the table. i. ii. in. iv. v. Observed abs. temperature. Reduced heat of galvanometer. yC X io'° Calc. abs. temp. Tubs. leak’. 371'1 156 127-0 374-6 -1-5° 492-5 638 1240 492-0 +0-5 723-0 3,32° 124-8 724-3 -i'3 745-o 3,810 126-6 749-1 -4-1 Sio-o 5> !5° 121-6 806-5 +3-5 — 6,910 123-3 867-1 +0-9 — 44,7oo 124-2 1379-0 — r — 57,400 123*1 1468-0 + 2 — 60,600 120-9 1488-0 + 9 i535'o 67,800 I22‘3 I53I-0 +4 Mean .... 123-8 Column I. gives the thermometrically measured absolute temperature of the black body; Column II. the excursions of the galvanometer, which are directly proportional to the radia- tion ; Column V. the temperature calculated for each observa- tion, using the mean value of C. The values in Column V. show that the deviations are small and without bias. The constant C is a natural constant of great importance ; its numerical value, according to Kurlbaum, is 5*32 x ro'r’ ergs, per square centimetre per second. By its means the calorimetrically measured radiation of bodies din be used to calculate their temperatures.1 So much for the total radiation. We now have to consider the spectral distribution of the energy in its relation to temperature. The facts obtained experimentally (and theoretically) for black radiation are most easily expressed graphically. The accom- panying curves show the results obtained by Lummer and Pringsheim for the distribution of energy in the normal2 1 Cf. O. Lummer and E. Pringsheim, Verb, deutsch. phys. Ges., 1, 230 (1899) ; 3, 36 (1901). - A normal spectrum is one in which the distance between two spectral colours is proportional to the difference of their wave-lengths. See E. C. C. Paly, Spectroscopy, p. 35.
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