6. Using the gamma-ray constant you calculate in (5), calculate the absorbed dose in bone 120 cm away from a 3-Ci 60Co point source for 10 minutes. There is a 2" wall (Pb) between the source and the target. Hint: use buildup factor for this poor geometry.

exposure rate in air: 2.70hrR

absorbed dose rate in air: 0.02357kgRJ

build up factor: 2.1

answer should be between 2.8-2.95 x10^-4 Gy