Question

An X-ray machine makes a picture of a broken arm (shown above)by sending high energy photons through an object that is opaque to visible wavelengths and measures the relative intensity of the X-rays that emerge on the other side. Denser substances, such as bone, absorb more photons than less dense substances and thus show up differently.

Material Absorption length

Air 3.4m

Fat 0.052m

Water 0.047m

Bone 0.017m

a. Consider the table of X-ray absorptions shown above. Near the center of an arm, the X-rays pass through 3.4 cm of muscle, 3.3 cm of bone, and 2.8 more cm of muscle. What fraction of the incident X-rays get through this part of the arm? (Hint: assume muscle has the same x-ray stopping power as fat.)

b. Assume now that the same beam of X-rays pass through an adjoining portion of the arm (say, directly between the two bones seen), so the path through the arm is the same but the X-rays are only going through muscle and fat. What fraction of the incident X-rays pass through this part of the arm?

Answer 1