According to the inverse square law, if you double the distance from the patient, how is the radiation dose affected?

According to the inverse square law, if you double the distance from the patient, how is the radiation dose affected?

• A. Dose is quadrupled
• B. Dose is halved
• C. Dose is reduced by four times
• D. Dose remains the same

Answer: (C)

Doubling the distance from the radiation source to the patient reduces the dose by a factor of four because the inverse square law states that intensity falls with the square of the distance (I ∝ 1/d^2). When distance doubles, the denominator becomes 4, so the dose becomes one quarter of its original value—i.e., it is reduced by four times. This is why the correct description is that the dose is reduced by four times.

Doubling the distance from the radiation source to the patient reduces the dose by a factor of four because the inverse square law states that intensity falls with the square of the distance (I ∝ 1/d^2). When distance doubles, the denominator becomes 4, so the dose becomes one quarter of its original value—i.e., it is reduced by four times. This is why the correct description is that the dose is reduced by four times.