THE ABSORPTION OF LIGHT PASSING THROUGH 
DEEP SLITS AS A FUNCTION OF THE LENGTH 
AND DEPTH OF THE SLITS AND OF THE 
WAVE LENGTH OF THE LIGHT 
{Abstract) 
L. P. SIEG AND A. T. FANT 
As indicated by Rayleigh, ^ practically every slit is a “Deep’^ 
slit, and a “Thin” slit can be obtained only with the greatest diffi- 
culty. Rayleigh used for the latter a fine scratch in a thin silver 
film deposited upon glass. In the present work ^ experiments were 
made with a series of slits with steel jaws, varying in depth from 
that of the thin safety razor blades to approximately 2.5 cm. The 
intensity of the transmitted light was experimentally determined 
as a function of the width and depth of the slits, and of the wave 
length of the light. For narrow slits, the narrowness depending 
upon the depth and wave length, practically complete polarization, 
with the electric vector parallel to the length of the slit, was noted, 
but exact measurements were deferred to a later work. On the 
basis of diffraction, multiple reflections, and the alteration of the 
ratios of the two electric vectors due to the latter, a simple theory 
is developed, the results of which agree well with the experimental 
results. The chief fact derived from the experiments is that for 
narrow slits the total amount of light transmitted is not, even ap- 
proximately, proportional to the opening, and that therefore the 
use of such slits for photometric purposes will lead, unless proper 
corrections are made, to erroneous values for the intensity of the 
transmitted light. 
The State University oe Iowa 
1 Roy. Soc. Eond. Proc. A, 89, 1913-14, p. 194. 
2 Full report in May, 1921, number of Jour, of Opt. Soc. of Amer. 
