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The visibility of radiation
NOTES
FROM THE
NELA
RESEARCH" LABORATORY.*
VISIBILITY 09" R A D I A T I O N .
By Edward P. Hyde, W. E. Forsythe and i~. E. Cady.
IN connection with an investiga,tion of the brightness of a black b o d y at various temperatures, it was desired to check the observations against values derived by computation, using the Planck energy equation and visibility data. As the only recent experiments on the latter have all been made by the use of the flicker p~otometer and as there is evidence that results by this method are at variance with those obtained by the method of direct comparison .ordinarily used in photometry, possibly because of inherent differences and possibly due to condi~tions imposed in the flicker method such as restricted field size, it seemed desirable to obtain new data on the visi,bjlity function b,y the direct comparison method under conditions comparable with those obtaining in ,the black-body brightness determinations referred to above. The distinguishing characteristics of the investigation; apart from the employment of the direct-comparison principle and from the conditions with respect to field size, etc., used~ in ordinary photometric praotice, are the use of the step-by-step method and the determination of the energy distribution in the spectrum. The steps chosen were so small (o.oo52 /, in the red to o.oo22/* in the blue) that the hue difference while appreciable, did not cause any decided difficulties in making ~t:he settings. The energy was evaluated by determining the color temperature of the source, and computing the distribution by means of Planck's. equation, allowing for dispersion and absorption l)y the optical system, and for scattered light. In ,this way the relative energy entering the eye in the different parts of the spectrum was readily determined. The apparatus employed consisted in an ordinary Lummer and Brodhun spectrophotometer provided with a special slit which could ,be moved a definite fixed amount, o.15 mm., in order to * Communicated by the Director. 859
830
NELA RESEARCH
LABORATORY NOTES.
[J, F, I.
provide the means for the shift of one spectrum with respect to the o.ther, this procedure being required to carry out the step,-bystep method. As a source a flat filament tungsten lamp, was used, operating at a color temperature appro.ximately 2o45 ° K. Measurements were made by 29 observers and the 29 luminosity curves obtained, after reducing them to. the same area, were averaged at each wave-length. The results are given in Column 2 of Table I. The relative average visibility data. were reduced on the basis of equal areas of the luminosity curves for the chosen color temperature (approximately 2o45 ° K.). The results of o.ther recent investigators are also included. TABL~ I.
Data on Relative Visibility. WaveLength. o.5o~ •51 •52 .53 .54 .55 .56 .57 •58 •59 .6o .61
Hyde Porsythe Cady. 0.328 .515 .698 .847 .968 .996 .995 .944 .855 .735 .6oo .464 .341 .238 .154
Ives Kingsbury. o.318 .473
. Nutting. * o.314 .456 .637 .646 .8Ol .815 .915 .925 .988 .986 .996 .995 .947 .949 .859 .871 .758 .762 .653 .634 -534 .498 .62 .396 .368 •63 .283 .268 •64 .183 .166 .65 .O95 .IIO .lO5 .66 .052 .068 ~58 *Revised values kindly furnished by Doctor Nutting.
Coblentz Emerson. o.316 .503 .71o .862 .954 .994 .998 .968 .898 .800 .687 .557 .427 .302 .194 .115 .0642
Reeves, 0.275 .474 .686 .841 -935 ,993 .985 935 .836 .71o .580 .446 .319 .214 .14o
In addition to the investigation just described a supplementary investigation of the relative visibility was made, using the same spectral pyrometer and method as-previously used for studying this function in the red and blue ends of the spectrum} Te~l out of the twen,~y-nine observers participated, and the results form a curve somewhat flatter near the centre and dropping off more rapidly towards the two ends of the spectrum. The previously 1Astrophys. Jour., 42, p. 28.6, 1915. Phys. Rev. (2) i I , p. 327, 1918.
June, I918. ]
NELA RESEARCH LABORATORY NOTES.
83I
obtained d a t a in the red and blue ends of the s p e c t r u m fit nicely on the ends of this curve. I n T a b l e I I are g i v e n d a t a r e c o m m e n d e d by t h e a u t h o r s on relative visibility c o v e r i n g practically the entire visible spectrum. T h e values f r o m o.5o ~ to o.64 a r e those given in C o l u m n 2 of T a b l e I. F o r the: red end a r e chosen ,the p r e v i o u s l y published d a t a of H y d e a n d F o r s y t h e b r o u g h t into a g r e e m e n t with the central region of the c u r v e at o.64 ~. F o r the blue end the published data of H a r t m a n h a v e been chosen as the best. TABLE II. Relative Visibility Data for Entire Spectrum. WaveLength.
Relative Visibility.
Wave Length.
Relative Visibility'.
WaveLength.
Relative Visibility.
o.4o~ •41 .42 •43
0.00oo9 .0006 2 .0041 .oi I ~
o.52~ .53 .54 .55
0.698 .847 .968 .996
o.64~ .65 .66 .67
o.154 .o94 .05I .026
•44
.o22
.56
.995
.68
.oi2
•45 .46 •47 •48 •49 •50
.036 .055 .087 .I38 .216 .328
.944 .855 .735 .60o .464 .34I
.69 .70 .71 .72 -73 .74
.oo6 2 .003 .ooi .0o07 :ooo3 o .oooI s
•51
,515
.57 .58 .59 .6o .6I .62 .63
.238
-75
.00OO9
.76
.00005
~ELA RESEARCH LABORATORY,
National Lamp Works of General Electric Company, Nela Park, Cleveland, Ohio, May, 1918.
The Action of Bleaching Agents in Fibres.
J.M.
~V~ATTHEWS.
(Color Trade Journal, through Paper, vol. 21, p. I3, November 28, I 9 1 7 ) . - - B l e a c h i n g in its general sense may be considered as a decoloration, or, more properly speaking, a destruction of the natural coloring matter which may be present in the substance under treatment. This is in contradistinction to the term " stripping," which is used in cases where the color from a dyed material is removed. All Of the textile fibres, whether of animal or vegetable origin, possess more or less coloring matter or pigment in their composition. Wool, for instance, with its congener hair is known to exist in a number of Colors, varying f r o m a pale yello.w to a deep brown or black, Even ordinary." white " w o o l has:a slightly yelloWish cast on scouring-0uti due.tO the presence o f a natural organic pigment in the fibre. In the l a r g e m a j o r l t y of cases the presence :of natural coloring matter in the fibre is not appreciably detrimental to the Color to be p r o d u c e d b y
FROM THE
NELA
RESEARCH" LABORATORY.*
VISIBILITY 09" R A D I A T I O N .
By Edward P. Hyde, W. E. Forsythe and i~. E. Cady.
IN connection with an investiga,tion of the brightness of a black b o d y at various temperatures, it was desired to check the observations against values derived by computation, using the Planck energy equation and visibility data. As the only recent experiments on the latter have all been made by the use of the flicker p~otometer and as there is evidence that results by this method are at variance with those obtained by the method of direct comparison .ordinarily used in photometry, possibly because of inherent differences and possibly due to condi~tions imposed in the flicker method such as restricted field size, it seemed desirable to obtain new data on the visi,bjlity function b,y the direct comparison method under conditions comparable with those obtaining in ,the black-body brightness determinations referred to above. The distinguishing characteristics of the investigation; apart from the employment of the direct-comparison principle and from the conditions with respect to field size, etc., used~ in ordinary photometric praotice, are the use of the step-by-step method and the determination of the energy distribution in the spectrum. The steps chosen were so small (o.oo52 /, in the red to o.oo22/* in the blue) that the hue difference while appreciable, did not cause any decided difficulties in making ~t:he settings. The energy was evaluated by determining the color temperature of the source, and computing the distribution by means of Planck's. equation, allowing for dispersion and absorption l)y the optical system, and for scattered light. In ,this way the relative energy entering the eye in the different parts of the spectrum was readily determined. The apparatus employed consisted in an ordinary Lummer and Brodhun spectrophotometer provided with a special slit which could ,be moved a definite fixed amount, o.15 mm., in order to * Communicated by the Director. 859
830
NELA RESEARCH
LABORATORY NOTES.
[J, F, I.
provide the means for the shift of one spectrum with respect to the o.ther, this procedure being required to carry out the step,-bystep method. As a source a flat filament tungsten lamp, was used, operating at a color temperature appro.ximately 2o45 ° K. Measurements were made by 29 observers and the 29 luminosity curves obtained, after reducing them to. the same area, were averaged at each wave-length. The results are given in Column 2 of Table I. The relative average visibility data. were reduced on the basis of equal areas of the luminosity curves for the chosen color temperature (approximately 2o45 ° K.). The results of o.ther recent investigators are also included. TABL~ I.
Data on Relative Visibility. WaveLength. o.5o~ •51 •52 .53 .54 .55 .56 .57 •58 •59 .6o .61
Hyde Porsythe Cady. 0.328 .515 .698 .847 .968 .996 .995 .944 .855 .735 .6oo .464 .341 .238 .154
Ives Kingsbury. o.318 .473
. Nutting. * o.314 .456 .637 .646 .8Ol .815 .915 .925 .988 .986 .996 .995 .947 .949 .859 .871 .758 .762 .653 .634 -534 .498 .62 .396 .368 •63 .283 .268 •64 .183 .166 .65 .O95 .IIO .lO5 .66 .052 .068 ~58 *Revised values kindly furnished by Doctor Nutting.
Coblentz Emerson. o.316 .503 .71o .862 .954 .994 .998 .968 .898 .800 .687 .557 .427 .302 .194 .115 .0642
Reeves, 0.275 .474 .686 .841 -935 ,993 .985 935 .836 .71o .580 .446 .319 .214 .14o
In addition to the investigation just described a supplementary investigation of the relative visibility was made, using the same spectral pyrometer and method as-previously used for studying this function in the red and blue ends of the spectrum} Te~l out of the twen,~y-nine observers participated, and the results form a curve somewhat flatter near the centre and dropping off more rapidly towards the two ends of the spectrum. The previously 1Astrophys. Jour., 42, p. 28.6, 1915. Phys. Rev. (2) i I , p. 327, 1918.
June, I918. ]
NELA RESEARCH LABORATORY NOTES.
83I
obtained d a t a in the red and blue ends of the s p e c t r u m fit nicely on the ends of this curve. I n T a b l e I I are g i v e n d a t a r e c o m m e n d e d by t h e a u t h o r s on relative visibility c o v e r i n g practically the entire visible spectrum. T h e values f r o m o.5o ~ to o.64 a r e those given in C o l u m n 2 of T a b l e I. F o r the: red end a r e chosen ,the p r e v i o u s l y published d a t a of H y d e a n d F o r s y t h e b r o u g h t into a g r e e m e n t with the central region of the c u r v e at o.64 ~. F o r the blue end the published data of H a r t m a n h a v e been chosen as the best. TABLE II. Relative Visibility Data for Entire Spectrum. WaveLength.
Relative Visibility.
Wave Length.
Relative Visibility'.
WaveLength.
Relative Visibility.
o.4o~ •41 .42 •43
0.00oo9 .0006 2 .0041 .oi I ~
o.52~ .53 .54 .55
0.698 .847 .968 .996
o.64~ .65 .66 .67
o.154 .o94 .05I .026
•44
.o22
.56
.995
.68
.oi2
•45 .46 •47 •48 •49 •50
.036 .055 .087 .I38 .216 .328
.944 .855 .735 .60o .464 .34I
.69 .70 .71 .72 -73 .74
.oo6 2 .003 .ooi .0o07 :ooo3 o .oooI s
•51
,515
.57 .58 .59 .6o .6I .62 .63
.238
-75
.00OO9
.76
.00005
~ELA RESEARCH LABORATORY,
National Lamp Works of General Electric Company, Nela Park, Cleveland, Ohio, May, 1918.
The Action of Bleaching Agents in Fibres.
J.M.
~V~ATTHEWS.
(Color Trade Journal, through Paper, vol. 21, p. I3, November 28, I 9 1 7 ) . - - B l e a c h i n g in its general sense may be considered as a decoloration, or, more properly speaking, a destruction of the natural coloring matter which may be present in the substance under treatment. This is in contradistinction to the term " stripping," which is used in cases where the color from a dyed material is removed. All Of the textile fibres, whether of animal or vegetable origin, possess more or less coloring matter or pigment in their composition. Wool, for instance, with its congener hair is known to exist in a number of Colors, varying f r o m a pale yello.w to a deep brown or black, Even ordinary." white " w o o l has:a slightly yelloWish cast on scouring-0uti due.tO the presence o f a natural organic pigment in the fibre. In the l a r g e m a j o r l t y of cases the presence :of natural coloring matter in the fibre is not appreciably detrimental to the Color to be p r o d u c e d b y