If 5000 persons were exposed to a background radiation of 0.1 rem per year, what would this represent in person-rem exposure?

To determine the person-rem exposure from the given background radiation scenario, you need to calculate the total exposure for all individuals. Person-rem is a unit that represents the dose of radiation exposure multiplied by the number of individuals experiencing that exposure.

In this case, if each of the 5000 individuals is exposed to a background radiation of 0.1 rem per year, the calculation would be as follows:

1. Multiply the radiation exposure per person (0.1 rem) by the total number of individuals (5000):

[

0.1 , \text{rem/person} \times 5000 , \text{persons} = 500 , \text{person-rem}

]

This calculation shows that the total exposure for that group is 500 person-rem. Therefore, the correct answer is 500, as it accurately reflects the sum total of radiation exposure experienced by the large group of individuals.