How can people protect themselves against irradiation from an external source?
When a person is exposed to irradiation from an external source, the radiation dose received is equal to the product of the dose rate (dose received in the unit of time) multiplied by the time during which the person is exposed to radiation. On the other hand, the dose rate at a point is proportional to the radiation flow at that point, and this flow decreases on withdrawal from the radiation source according to the product of two other factors; the first follows the law of decrease with the square of the distance, i.e. although the radiation is not absorbed on its path from the source to the object of irradiation, the dose rate would decrease in inverse proportion to the square of the distance to the emitting focus, in this case a point source. In addition, the radiation is partially absorbed by the medium placed between emitter and receiver, which means that the second factor of dose rate decrease as a function of distance follows an exponential law. As a result of the above, protect
