Question

Empirical results have revealed that for every unit of radiation dose (1 rad) there are 5 ✕ 10¹¹ inactivating events per cubic centimetre treated.

(a)If one were to administer a dose of 12 millirads, how many inactivating events per cubic centimetre would this dose produce?

inactivating events per cubic centimetre

(b)The approximate volume of a cell is estimated to be 10⁻¹¹ cm³. Calculate the fraction of the cells of the tissue treated by X-rays that will be hit if we allow only one event per cell? (Enter your answer as a percentage.)

| -/16.66 points v ZINPHYSLS3 24.P.011. My Notes Ask Your Teacher V Empirical results have revealed that for every unit of radiation dose (1 rad) there are 5 x 1011 inactivating events per cubic centimetre treated. (a) If one were to administer a dose of 12 millirads, how many inactivating events per cubic centimetre would this dose produce? inactivating events per cubic centimetre (b) The approximate volume of a cell is estimated to be 10-11 cm3. Calculate the fraction of the cells of the tissue treated by X-rays that will be hit if we allow only one event per cell? (Enter your answer as a percentage.) % eBook

Answer 1

a. 1 milli radian = 1/1000 radians

12 milli radian = 12/1000 radians

According to question 1 radian = 5 x 1011  inactivating events/ cm3

So 12 milli radian = (12/1000) * 5 x 1011 inactivating events / cm3

= 6 x 109 inactivating events / cm3  

b. Considering that 1 radian dose is administered,

Volume of a cell = 10-11  cm3  

Number of inactivating events per cell = 10-11 * 5 x 1011 = 5 inactivating events per cell

However it is said to assume that the inactivating events be taken as 1 per cell.

Fraction of cells affected = (1/5) * 100 = 20 %