(a) Suggest two causes of lack of sharpness of an X-ray image. (b) The thickness of a sheet of metal is examined using a parallel X-ray beam, as illustrated in [Figure 12.1]. Part of the beam passes normally through the metal of thickness 3.2 mm. Another part of the beam passes normally through the metal of thickness x mm. The linear attenuation (absorption) coefficient for the X-ray beam in the metal is 1.5 cm⁻¹. The ratio intensity of X-ray beam transmitted through 3.2 mm of metal intensity of X-ray beam transmitted through x mm of metal is found to be 0.81. (i) Calculate the thickness x. x = .............................................................. mm (ii) The ratio of the intensities is also the ratio of the powers of the X-ray beams. Calculate this ratio in decibels. ratio = .............................................................. dB