A small air-filled cavity ion chamber has copper walls with thickness equal to the maximum electron range. The cavity volume is 0.100 cm3, the air density is 0.001293 g/cm3, and a given y-ray exposure generates a charge (either sign) of 7.00 x 10-10 C.

(a) What is the average absorbed dose in the cavity air?

(b) Apply B-G theory to estimate the absorbed dose in the adjacent copper wall, assuming a mean energy T-0.43 MeV for the cavity-crossing electrons.

(c) Suppose T is 34% in error and should have the value 0.65 MeV. Redo part (b). What was the resulting percentage error in Dcu?