If the original technique is 20 mAs at 80 kVp, which of the following would produce double the IR exposure?

To achieve double the image receptor (IR) exposure while keeping the kilovolt peak (kVp) constant at 80, adjusting the milliampere-seconds (mAs) is necessary. In radiography, the amount of radiation exposure to the IR is primarily controlled by the mAs.

The relationship between mAs and IR exposure is direct; doubling the mAs will approximately double the exposure. Starting from the original setting of 20 mAs, if we want to double that exposure, we would need to increase the mAs to 40. This means using 40 mAs at the same 80 kVp would yield approximately twice the exposure compared to the original technique of 20 mAs at 80 kVp.

The other options either maintain the original mAs or do not increase it sufficiently to achieve the desired doubling effect. Thus, by adjusting to 40 mAs, the correct choice effectively doubles the IR exposure.