If distance from a radiation source is doubled, dose rate changes by which factor?

If distance from a radiation source is doubled, dose rate changes by which factor?

• A. Dose rate decreases by a factor of two.
• B. Dose rate stays the same.
• C. Dose rate decreases by a factor of four.
• D. Dose rate increases.

Answer: (C)

Radiation dose rate from a point source follows the inverse square law: the intensity at a given point is proportional to 1 divided by the distance squared. When you double the distance, the dose rate becomes one quarter of its original value because (2)^2 = 4. So the dose rate decreases by a factor of four. This assumes there’s no added shielding or other factors altering the path of the radiation.

Radiation dose rate from a point source follows the inverse square law: the intensity at a given point is proportional to 1 divided by the distance squared. When you double the distance, the dose rate becomes one quarter of its original value because (2)^2 = 4. So the dose rate decreases by a factor of four. This assumes there’s no added shielding or other factors altering the path of the radiation.