6. A narrow beam of 10,000 photons per second is normally incident on a 6 mm aluminum

sheet. The beam consists of equal numbers of 200 keV photons and 2 MeV photons. (a)

Calculate the number of photons per second of each energy that are transmitted without

interaction through the sheet. (b) How much energy is removed from the beam per second

by the sheet? (c) How much energy is absorbed in the sheet per second?

7. A source of 1 MeV gamma rays produces a uniform flux of 106 photons/cm²*s at a distance

of 150 cm. (a) What is the absorbed dose rate at that distance? (b) What is the absorbed

dose rate at 2 m?

8. A planar disk source with a diameter of 200 cm emits 662 keV gamma rays with strength (SA)

of 107 y/cm²*s. What is the dose rate to air at a point 5 cm over the centerline of the disk?

9. A 2 Ci ¹37 Cs point source is placed at the center of a spherical (R=10 cm) lead shield. Calculate

the photon flux 50 cm away from the point source, considering photon attenuation in air./n10. What thickness of lead is required to attenuate a broad beam of 500 keV photons to one half

of the original number? Be sure to use appropriate buildup factors!