If 12 mAs produce appropriate IR exposure at 36 inches SID, how much mAs is needed at 72 inches SID to maintain that amount of exposure to the IR?

Question

Quizplus · Accepted Answer

The exposure to the image receptor (IR) is inversely proportional to the square of the distance (SID). Doubling the distance from 36 inches to 72 inches requires four times the mAs to maintain the same exposure, so 12 mAs x 4 = 48 mAs.

If 12 MAs Produce Appropriate IR Exposure at 36 Inches