13. Suppose that a person who has one hand in a uniform beam of x rays receives a dose of 90 millirem (mrem) in 30 s. This per- son now puts both hands side by side in the beam for 30 s. Assuming that...

Extracted text: 13. Suppose that a person who has one hand in a uniform beam of x rays receives a dose of 90 millirem (mrem) in 30 s. This per- son now puts both hands side by side in the beam for 30 s. Assuming that the beam is wide enough to cover both hands equally, the radiation dose she will now receive is A. 180 mrem, since twice the number of atoms will be exposed. B. 90 mrem, since the number of exposed atoms per gram is unchanged. C. 45 mrem, since the radiation is spread over twice as much of her body.