Which action is most effective to reduce exposure?

• A. Increase time near source
• B. Increase distance
• C. Remove shielding
• D. Turn off the dosimeter

Answer: (B)

Exposure decreases very quickly with distance from the source because of the inverse-square law: doubling the distance cuts the dose rate to about one quarter. This makes increasing distance the most effective single action to reduce exposure quickly, since the same amount of scattered or direct radiation becomes much less intense as you move away. Reducing time near the source also lowers dose, but the reduction gained from distance can be much larger in many situations. Shielding can help, but its benefit depends on the material and thickness available, so it isn’t as universally powerful as simply stepping back. Turning off the dosimeter doesn’t reduce the amount of radiation you’re receiving; it only stops the device from recording it.