Suggest two causes of lack of sharpness of an X-ray image.
The thickness of a sheet of metal is examined using a parallel X-ray beam, as illustrated in the figure below.
(not drawn to scale)
Part of the beam passes normally through the metal of thickness 
. Another part of the beam passes normally through the metal of thickness 
. The linear attenuation (absorption) coefficient for the X-ray beam in the metal is 
. The ratio
is found to be 0.81.
Calculate the thickness 
The ratio of the intensities is also the ratio of the powers of the X-ray beams. Calculate this ratio in decibels.
.
.
