450 Minchin — Reflection of Light by Colored Papers. 



The intensity of the light reflected by the light red paper 

 was very low and it was necessary to narrow T to 0*l mm . A 

 match was then obtained for red and blue. 



The green papers reflected all colors in considerable amounts. 

 The dark green reflected red and green light about equally, 

 while the light green reflected less of the red and reflected 

 green and blue in about the same amounts, but as the inten- 

 sity of the light admitted at T was increased more blue than 

 green was reflected. 



The dark blue paper reflected red light of an intensity about 

 two and one-half times the intensity of the blue reflected. 

 The other colors were reflected in very small amounts. 



With the light blue paper all the colors were reflected when 

 the intensity at T was 0*1 or 0*2, and with intensities at T of 

 0'4 and 0*5 a match was obtained with violet light only. 



A comparison of all the papers used can be made only for 

 an intensity of light admitted at T of 0*1. The following 

 table gives the width of T' in terms of T for a match in the 

 different colors. For example, in the red when light was 

 admitted directly, T r was 0*21 times the width of T for match, 

 when the mirror was used T / was 0*41 times the width of T, 

 etc. 



T' in terms of T. 



Colors. 



Light from. , K v 



Eed. Yellow. Green. Blue. Violet. 



Direct... 0*21 0-21 0-23 0-28 0*24 



Mirror 0'41 0*42 0*46 0*55 0*47 



Deep red 6-44 ? ? ? ? 



Light red 4*60 ? ? 22*34 ? 



Dark green 9*52 13-25 905 15*61 12*09 



Dull green 14*24 13*02 1056 14*50 ? 



Light green 12*89 11*76 6*83 7*82 ? 



Dark blue 9*24 ? ? 23*34 ? 



Light blue 12*13 10*88 9*36 7'89 10*36 



The dark green and the light blue papers are the only papers 

 that reflected all colors sufficiently to obtain a match. The 

 light green and the dull green papers are the next in order, 

 both the latter reflected very little violet light. The light 

 reflected by the dark green and the light blue papers is more 

 nearly white light than that from any of the other papers used. 



Less than 0'02 of the incident light was reflected by the best 

 paper used, when all conditions were the best possible. 



The observations embodied in this paper were made in the 

 Physical Laboratory of the University of Michigan, at the 

 suggestion of Professor Peed, to whom thanks are due for his 

 interest and assistance during the progress of the investigation. 



Physical Laboratory, University of Koehester, January, 1905. 



