*1-13 What voltage must be applied to a molybdenum-target tube in order that the emitted x-rays excite K fluorescent radiation from a piece of copper placed in the x-ray beam? What is the wavelength of the fluorescent radiation? In Problems 14 and 15 take the intensity ratios of Ka to K in unfiltered radiation from Table 1-1. 1-14 Suppose that a nickel filter is required to produce an intensity ratio of Cu Ka to Cu K of 100/1 in the filtered beam. Calculate the thickness of the filter and the trans- mission factor for the Cu Ka line. *1-15 Filters for Co K radiation are usually made of iron oxide (Fe2O3) powder rather than iron foil. If a filter contains 5 mg Fe2O3/cm, what is the transmission factor for the Co Ka line? What is the intensity ratio of Co Ka to Co K in the filtered beam? 1-16 A copper-target x-ray tube is operated at 40,000 volts and 25 mA. The efficiency of an x-ray tube is so low that, for all practical purposes, one may assume that all the input energy goes into heating the target. If there were no dissipation of heat by water- cooling, conduction, radiation, etc., how long would it take a 100-gm copper target to melt? (Melting point of copper 1083C, mean specific heat = 6.65 cal/mole/C, latent heat of fusion 3220 cal/mole.) *1-17 Assume that the sensitivity of x-ray film is proportional to the mass absorption coefficient of the silver bromide in the emulsion for the particular wavelength involved. What, then, is the ratio of film sensitivities to Cu Ka and Mo Ka radiation?