Question

An 80-kg person whose surface area is 1.30 m² worked for two hours at a distance of 2.0 meters from a spherically-symmetric source of radiation whose output power is 0.35 W. What dose (in rads) did he receive?

A) 67

B) 29

C) 56

D) 41

E) None of these

Answer 1

The fraction of fluence radiation or the power recieved by person is given by

F= (surface area of person)/ (4 r2)

F= 1.3/(4*3.14*22) = 0.02587

the power recieved by person is given by

P= 0.35* 0.02587= 0.90545810-3 W= 0.90545810-3 J/s

power recived per Kg will be , (but J/kg is equals to Gray), hence the dose per sec

D =(0.90545810-3 )/ 80=1.1318 *10-4 J/Kg*s (Gy/sec)

D = 1.1318 *10-4 Gy/sec

1Gy= 100 Rad and 1hr=3600 sec

D = 1.1318 *10-4 *100 *3600 = 40.75 Rad/hr =41 Rad/hr

Answer will be D