. The American journal of roentgenology, radium therapy and nuclear medicine . the filmswere kept in constant irregular motion toinsure uniformity of development^ As statedpreviously, the degree of development of thefilm has no effect upon the values obtained;the chief consideration is that each filmreceive uniform development over its wholesurface. For each set of conditions six ormore films were exposed (unless otherwisespecified) and the average A^alue obtained ofthe ratio of the diffuse to the total radiationreaching the film. The effects of diaphragms,thickness of scattering material, tub
. The American journal of roentgenology, radium therapy and nuclear medicine . the filmswere kept in constant irregular motion toinsure uniformity of development^ As statedpreviously, the degree of development of thefilm has no effect upon the values obtained;the chief consideration is that each filmreceive uniform development over its wholesurface. For each set of conditions six ormore films were exposed (unless otherwisespecified) and the average A^alue obtained ofthe ratio of the diffuse to the total radiationreaching the film. The effects of diaphragms,thickness of scattering material, tube-voltageand filters (between the scattering materialand film) upon the ratio were 3 shows examples of the curvesobtained of density plotted against exposuretime. The film giving these curves was ex-posed through six inches of water with the senting the fog density, or the density of theunexposed portions of the film. It will benoted, however, that the densities fromdiffuse radiation are not much less than thoseproduced by the total radiation. At several. EXPOSURE 40 SEC. Fig. 3. Curves of density of film plotted against ex-posure time. Curve i is for the total radiationreaching the film, and Curve 2 the diffuse radia-tion in the shadow^ of the lead disk. Conditions;6 inch depth of water (i2x 12 inches) as the scat-tering material, 20 inch target-film distance, 5 inchspark-gap, milliamperes. F represents the fogdensity, or the density of the unexposed portionsof the film. TABLE I PATA TAKEN FROM CURVES OF FIGURE 3 Density of Film Exposure to Exp osure to Ratio of Total Radiation Diffuse Radiation Exposures in Seconds in Secon ds Et D Et Ed Ei> T .84 1-3 154 ■85 23-9 .84 1-9 259 31-3 ■83 33-2 &2 Mean .84 tube running at 5 inch spark-gap and The exposures varied from 10to 40 seconds. The densities of Curve i wereproduced by the total radiation reaching thefilm, while the densities of Curve 2 were
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