Radiation Safety Practice Exam

How much radiation exposure is equivalent to four feet of distance using the inverse square law?

1. 500 mREM/hour

2. 125 mREM/hour

3. 31 mREM/hour

4. 56 mREM/hour

The correct answer is: 31 mREM/hour

The correct answer is based on the application of the inverse square law, which states that the intensity of radiation (or any form of wave propagation) is inversely proportional to the square of the distance from the source. When considering how much radiation exposure is experienced at different distances, this principle helps us calculate the reduction in exposure as one moves away from the source. To apply the inverse square law, you would typically use the formula: \[ I_1/I_2 = (D_2^2)/(D_1^2) \] where \( I \) represents the intensity at different distances \( D \). In the scenario provided, if we start from an initial intensity (I1) at a certain distance (D1) and want to find the new intensity (I2) at four feet farther away (D2), the formula allows us to compute how the intensity decreases as we increase distance. For example, if the original intensity is assumed to be 500 mREM/hour at 1 foot, according to the inverse square law, moving to 4 feet away means: \[ I_2 = I_1 \times (1/4^2) \] Calculating this gives 500 mREM/hour ×