Which of the following is used to determine RF exposure from a transmitted signal?
Why An RF exposure evaluation combines all three factors. Duty cycle matters because the FCC limits are based on time-averaged exposure (6 minutes for controlled, 30 minutes for uncontrolled), so a signal that is on only part of the time averages down. Frequency matters because the maximum permissible exposure limits change with frequency, being most restrictive around 30 to 300 MHz where the body absorbs energy most efficiently. Power density, usually expressed in mW/cm^2, is the actual quantity compared against those limits.
Watch out Each single-item choice names a real part of the calculation, but none of them alone tells you whether you are within the MPE limit; you need the field strength or power density, the frequency it occurs at, and how long it is present.
Exposure = how strong, at what frequency, for how much of the time. Miss one and the answer is incomplete.