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Figure 384

The four different parameters controlling the attenuation of X-rays in matter: the wavelength λ of the X-ray beam (the attenuation factor α [alpha] is proportional to λ3); the atomic number Z of the element the beam passes through (α is proportional to Z4); the mass density ρ of the matter the beam passes through (α is proportional to ρ); and the thickness η of the object to be radiographed (the variation of intensity of the transmitted X-ray ΔI/I is proportional to the difference of thickness Δη). The thinner the arrow below the object (the cube), the greater the attenuation of X-rays. See .