Which statements are true about the inverse square law? 1) The intensity varies inversely as the square of distance. 2) As you move closer to the X-ray source, the dose increases. 3) It is best to maximize the distance between the exposure source and the person.

• A. 1 and 2
• B. 1 and 3
• C. 2 and 3
• D. 1, 2, and 3

Answer: (B)

The inverse square law states that radiation intensity from a point source falls off with the square of the distance, so doubling the distance drops the intensity to one quarter. That means the dose rate at a person, assuming other factors are constant, also decreases as distance increases, since less energy is reaching them per unit time. So the statement that the intensity varies inversely as the square of distance is a direct expression of the law. Because dose is tied to that intensity, it follows that increasing the distance between the exposure source and the person reduces the dose, which is why maximizing distance is a primary safety principle. The idea that moving closer to the X-ray source increases the dose is a natural corollary of the same law—dose rises as distance decreases. In many exam contexts, the emphasis is on recognizing the 1/r^2 relationship and applying it to safety practice, which is why statements about the intensity-distance relationship and about increasing distance to minimize exposure are highlighted as true.