COLOR SENSITIVENESS OF PHOTO-ELECTRIC CELLS 
 
 BY 
 
 WILLIAM PARKERSON 
 
 B.A. Tulane University, 1919 
 
 THESIS 
 
 SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS 
 FOR THE DEGREE OF MASTER OF SCIENCE IN PHYSICS 
 IN THE GRADUATE SCHOOL OF THE UNIVERSITY 
 OF ILLINOIS, 1922 
 
 URBANA, ILLINOIS 
 

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^ yzz. _= 
 
 UNIVERSITY OF ILLINOIS 
 THE GRADUATE SCHOOL 
 
 J's-ins -192-^- 
 
 I HEREBY RECOMMEND THAT THE THESIS PREPARED UNDER MY 
 
 SUPERVISION BY WILIT.;.: ' PAn! <I^^S.QN 
 
 F.N'riTT.F.D COLOR EEVETTIV ^TI -'t^-P? ^7 - U-IC OFLI xU 
 
 BE ACCEPTED AS FULFILLING THIS PART OF THE REQUIREMENTS FOR 
 THE DEGREE OF L AST^R Q F SCIEH-CE — 
 
 Recommendation concurred in* 
 
 Committee 
 
 on 
 
 Final Examination* 
 
 Required for doctor’s degree but not for master’s 
 
Digitized by the Internet Archive 
 
 in 2015 
 
 https://archive.org/details/colorsensitiveneOOpark 
 
TABLE OF C05JTENTS 
 
 I INTRODUCTION ' . . . 
 
 Simple Cell, B’ig. la 
 
 II APPARATUS AND i\IANIPULATION .... 
 
 Optical System, Fig. lb 
 
 Arbitrary Scale, Fig. 3 
 
 Diagram of Connections, Fig.b. . 
 
 Ill CALCULATIONS AND RFSULTS 
 
 Data on cell KH No. 1 
 
 Data on cell KH No. 2 
 
 IV CONCLUSION 
 
 1 
 
 1 
 
 3 / 
 . b 
 
 4 
 
 5 
 
 6 
 8 
 9 
 
 10 
 

T. INTR0DUCTI05 
 
 Tns hi>^tc:-cy cf the phot ect ric srfect ,"it^ 
 
 discovery by Eertz, in 1887 that a" arc could ''-e strucV" --‘t -d'-i. o 
 
 terminals at a lower vcltage when a neio hbcr irp arc was ruuy.iih.-., 
 than -Alien the latter was shut off. In the follohin^ year Hallwaons 
 found that a "stallic pldtc, nes’atively char;yedj lost tnat chr.rp© 
 wnen exposed to ultra-violet li^ht. 7ince these two pioneer dis- 
 coveries , tne phenomenon of phot ■^-electricity has been studied oy 
 many invest igatcrSj frcai bctn a theoretical and a utilitarian point 
 of vie'... In this connection may be menticr-ed such - er as Lao-enour;^' j 
 rister and Geitsl, Lenard, Pchl and ^rinpsheim, aoid Buphes. 
 
 Finally^ a phot oel^-ctr ic cell hc^s oeen devaloped, whichj iu 
 its sii. olest f CT;.. j IS sii' A'jii o ;itical''-y iii Fip«ln. !■- ccnsi3.>si 
 
 r P - 
 
 O- WV gj 
 
 Fig. la 
 
 ^lass tube, clC'^ed at both ends, h:,vin_ a sp-i. et: oai :ulb at 
 the center. ?>-^ a-ol of this bnld is silvered, sc that, while sorv- 
 ing as negative terminal, it also operates to focus the i^oioent 
 lipht on ? is the positive terminal, consist i;:a cf a wire led ir 
 tiu'cuph oiae end cf the cell ahv* G ent in the for-.- of a cii'Oi e, -tcr^.-os 
 which t'.vc f iiier ,vir-es c-.,re strun;-; aiam;- c-cicaij-y . T;..aoe or .Sj -.''ires 
 arid the circle aoout the-i:. are covered .vith a thin lay.-r ot .--n al u.li 
 rmetal and the cell is sensitized by hydro^^en. A detailed dascrip- 
 tich of the ouha t r Lf ct 1 vjv. ana p- rea-.- Lot io.- cf su-on. je-j-xS ,,,c-.y 
 
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2 
 
 in the Physical Review, Vol.7, p 62, 1916. 
 
 If a potential difference be placed across tne terminals of 
 the cell when no light is incident upon it, no current will flowj 
 that is to say, the cell shows no ’’dark current”. On the other han 
 if light impinges upcn a cell, which has a difference of potential 
 between its terminals, a current will flow. If we consider the 
 coulombs of electricity which flow through the cell per erg of in- 
 
 cident light energy (the specific photc-electric sensitiveness), 
 this factor will be found to change very appreciably with the wave 
 length of the incident light. The color-sensitiveness curve for 
 the alkali metals, unlike that for other metals, possesses a reso- 
 
 nance peak in the violet end of the visible spectrum. The wave 
 length at which the maximum of this peak occurs shall be denoted by 
 ^max* Obviously, in any investigation, in which a photo-electric 
 cell is to be used as a iteasuring instrument, a thorough knowledge 
 of the characteristics of the cell is essential. Accordingly, cells 
 prepared in this laboratory by Dr. Kunz, to be used by Dr. Shelford 
 in certain experiments, were turned over to the writer for cali- 
 bration. The problem, then, was to collect the necessary data and, 
 with this data, to plot the color-sensitiveness curve for each of 
 these cells. 
 
 It should be clearly understood at the cutset, that no very 
 high degree of accuracy is claimed for the measurements of the spe- 
 cific photo-electric sensitiveness. The form of the curve and the 
 value of more important than the absolute values of the 
 
 specific photo-electric sensitiveness. 
 

 
 
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 II. ANr MAI'IIPULATIO:/ 
 
 Tne spectruai used in the /..i^asure.^ ent 3 , .vas oou^lnsd 
 
 optical syster;.^ shc/m dia^ro...:.r/.at ically in Fi'_.lo. F is a 
 
 
 larr.p which fnrniened a line source, nii^n candle power. Tp 
 and Dj are diaphra^Tos used to elifi:inats, as 'r--.r as possible, stray 
 light. Lp and Lg focused the light fro.r F_ at the slit. ^ served 
 to render the light parallel, and _L^ tc define the spectrum. 
 
 Ic was necessary tc icnc”' the energy distribution in tae 
 spectrurr. and also the wave length at every point in it. To effect 
 these calio 1 'o.t ions an arbitrary scale he.d to be cnO'Sen alcrn tne 
 spectrun.. This arbitrary scale Sy togeoher with the attacned slit 
 and table L and T, respectively, is shc-em dia.wra:id.ctically in Fig. 3. 
 This arrangement was placed just beyond (Fig. lb'' in such a posi- 
 tion txiat the lengtn iirection of the slit L (Fig. 2^ was perpen- 
 dicular to tne plane of the paper (Fig. lb) and so tnat by tu.rning R 
 (Fig. 3), L (Fig. 2) could be sniftea bach and forta in a direction 
 perpendicular to tne principal axis of (Fig. lb''. 
 
 A Hilger constant-deviat ion spectrometer ".as calibrated 
 with a Helium Pliioker tube. This sp.jvjorc„:et or was then used to 
 measure the wave length ct the light passing throu^^h L (Fig. 3} for 
 l<i points on tne arbitrary scale S (Fi.g.3). These points -tere so 
 
 cncssn that the wavs lermth ranoad frcr/, 400 uu '^o -600 
 
 
 

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6 
 
 III. CALCULATIOIMS AND RESULTS 
 
 ift 
 
 Tiiermo-pl,le Calibration .- According to F. Coblentz the 
 
 radiant energy at a distance of one meter from a Hefner lan;p is 
 
 26.0-10“^ g. cal. per sq.cm, per sec. when no diaphragmi is used. 
 
 Taking Joule's equivalent as 4.16? • lo"^ ergs per cal., this value 
 
 becomes 1089 ergs per sq.cmj. per sec. at one m'eter distance. The 
 
 thermo-pile was placed 75 cm. fromi the lamp and for this distance 
 
 the energy per sq.cm, per sec. is 
 
 100 . 
 
 1089(7^)2 = 193? ergs. 
 
 The average deflection of the galvanorj. at er was 63.41 mm. Hence, a 
 deflection of 1 mm. of the galvanometer corresponded to a flow of 
 energy of 
 
 1937 
 
 q 2 ""ai - 31.04 ergs per sq.cm, per sec. 
 
 Scale-wave-length Calibration . - The light passing through 
 L (Fig. 3) was, of course, not exactly monochromatic. Consequently, 
 for every setting of the scale S (Fig. 2), readings of the extreme 
 wavs lengths were taken ana tne average of these two extremes was 
 used as the mve length for that position. 
 
 Scale-energy Calibration .- The area of the slit L (Fig, 3) 
 was .2843 sq.cm. Therefore, the energy passing that slit for 1 mm. 
 of deflection of the galvanometer was 
 
 31.04 • .2842 = 8.826 ergs per sec. 
 
 The P h oto-electric Current .- The galvanometer used to 
 measure the photo- electric current had a sensitiveness of 2711 meg- 
 ohms. Its figure of merit was therefore 
 
 37ltlO"S = 2'®®® ■ 
 
 * Bulletin of Bureau of Standards. Voi.li,j3.g9, 1914 
 
V 
 
 I 
 
 
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 ' - ' 
 
 i • A , , , i 
 
Since the scale vvas 1.765 meters from tne mirror ^ 1 mm. deflection 
 
 indicated a current of 
 
 5.88S • 10"^*^ o i^-lO 
 
 “ 3.0899 • 10 amperes. 
 
 The data taken for the potassium hydride cells numbers 1 anc 
 2, are shown below in tabulated form. 
 
 Column No. 1 gives the scale readings. 
 
 Column Wo. 2 gives deflection of thermopile galvanometer in 
 miiiimet ers. 
 
 Column Wo. 3 gives energy in ergs per second. 
 
 Column No. 4 gives deflection of photoelectric galvanometer 
 in millimeters. 
 
 Column No. 5 gives photo-electric current in amperes x 10“^^. 
 
 Column No. S gives specific photo-electric sensitiveness in 
 coulombs per erg x 
 
 Column No. 7 gives wave length inyuyui . 
 

s 
 
 
 
 Table 
 
 I 
 
 
 
 
 
 
 Cell ZE 
 
 No. 1 
 
 
 
 
 
 
 Voltage on 
 
 Cell = 
 
 = 95. 2 
 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 412 
 
 2, 0 
 
 17.653 
 
 6 . 5 
 
 13. 584 
 
 . 7693 
 
 413. 5 
 
 415 
 
 2. 1 
 
 18. 535 
 
 9.0 
 
 18.809 
 
 1,0150 
 
 413.6 
 
 420 
 
 2.4 
 
 21. 182 
 
 16.0 
 
 33, 438 
 
 1,5790 
 
 418,6 
 
 425 
 
 3.8 
 
 33.539 
 
 29.3 
 
 61.234 
 
 1. 8260 
 
 425. 1 
 
 430 
 
 6.1 
 
 53. 339 
 
 51,3 
 
 107.212 
 
 1.9900 
 
 432. 0 
 
 435 
 
 9.4 
 
 82.964 
 
 89.2 
 
 186. 419 
 
 2.2470 
 
 439. 5 
 
 440 
 
 14.9 
 
 131. 507 
 
 153. 0 
 
 319. 755 
 
 3.4300 ' 
 
 CO 
 
 o 
 
 445 
 
 24.9 
 
 219. 767 
 
 233. 3 
 
 485.484 
 
 2.2100 
 
 459.8 
 
 450 
 
 39.5 
 
 346.627 
 
 378.0 
 
 580. 992 
 
 1.5666 
 
 473.9 
 
 455 
 
 62. 5 
 
 551.625 
 
 274. 0 
 
 572.833 
 
 1.0380 
 
 490.5 
 
 460 
 
 99. 5 
 
 878. 187 
 
 220. 0 
 
 459. 778 
 
 0.5333 
 
 509.5 
 
 465 
 
 160.2 
 
 1413.925 
 
 134.8 
 
 281.718 
 
 0.19S2 
 
 536.6 
 
 470 
 
 247.5 
 
 2184.435 
 
 59.2 
 
 123.722 
 
 0; 0663 
 
 571.0 
 
 475 
 
 355. 0 
 
 3133.230 
 
 20.4 
 
 42. 634 
 
 0.013S 
 
 617. 6 
 

Elcc^yic Scpsihii'e^css. 
 
9 
 
 T^ol s 
 
 
 
 Csll 
 
 TCH 
 
 
 
 Voltage 
 
 on C 
 
 1 
 
 
 3 
 
 4 
 
 413 
 
 3.0 
 
 17.653 
 
 3. 
 
 415 
 
 3.1 
 
 15.535 
 
 5. 
 
 430 
 
 2.4 
 
 31, 182 
 
 8. 
 
 425 
 
 3.8 
 
 33. 553 
 
 15. 
 
 430 
 
 6.1 
 
 53 . 833 
 
 26. 
 
 435 
 
 C' t 4 
 
 S3. 334 
 
 48. 
 
 440 
 
 14.3 
 
 131.507 
 
 85. 
 
 445 
 
 24.3 
 
 219. 737 
 
 148. 
 
 450 
 
 39. 5 
 
 348. S37 
 
 319. 
 
 455 
 
 62.5 
 
 551.625 
 
 268. 
 
 430 
 
 ^ SI 
 
 . 0 
 
 878. 187 
 
 252. 
 
 435 
 
 160.2 
 
 1413.925 
 
 230. 
 
 470 
 
 247.5 
 
 2184.435 
 
 114. 
 
 475 
 
 « 0 
 
 3133. 230 
 
 34. 
 
 = 130.5 
 
 5 
 
 6 
 
 7 
 
 7.942 
 
 0. 4438 
 
 413.5 
 
 10.867 
 
 0.5860 
 
 413.6 
 
 17.555 
 
 0.3350 
 
 418.6 
 
 33. 393 
 
 0.9650 
 
 425 . 1 
 
 54. 337 
 
 1.0080 
 
 433.0 
 
 100. 315 
 
 1.2090 
 
 439.5 
 
 179. 104 
 
 1.3610 
 
 44910 
 
 309. 3b5 
 
 1.4070 
 
 453.8 
 
 457. 68S 
 
 1. 3140 
 
 473.9 
 
 531. 138 
 
 1.0170 ■ 
 
 490.5 
 
 539.351 
 
 0.6710 
 
 509.5 
 
 461. 450 
 
 0.3253 
 
 533 . 3 
 
 359 . 293 
 
 0.1096 
 
 571.0 
 
 71.057 
 
 0.0227 
 
 S17.6 
 
 II 
 
 Wc 
 
 ell 
 
 6 
 
 3 
 
 4 
 
 5 
 
 0 
 
 0 
 
 7 
 
 0 
 
 0 
 
 5 
 
 0 
 
 8 
 
 5 
 
 0 
 
10 
 
 From the values found in the last two columns of the data 
 for each cell, the corresponding color-sensitiveness curve is ob- 
 tained. It may be seen frcir the curves that, for KH No.l, = 
 
 493yyx , and for I\H No. 3, ~ ^cSSyxyu., 
 
 IV, CONCLUSION 
 
 The work had to be done with extreme cars and at a time 
 when the atmosphere was cool and dry, to prevent leakage effects. 
 All the diagrams contained herein, with the exception of No. la, 
 have, by the kind permission of Miss F.F. Seiler, been taken from 
 her doctor’s thesis. 
 
 I take this occasicn tc express appreciation to Profes- 
 sor E. H. Williams and Professor Jakob Kunz for the interest taken 
 in my work and to thank Professor A.P. CarK.an for the use of the 
 lu'c oratory facilities.