Question
At which of the following frequencies does maximum permissible exposure have the lowest value?
Answer Options
- A) 3.5 MHz
- B) 50 MHz
- C) 440 MHz
- D) 1296 MHz
Correct Answer: B
Explanation
Maximum Permissible Exposure (MPE) limits are based on how efficiently the human body absorbs RF energy. The body acts like an antenna and tends to absorb the most energy when a person’s height is close to a half-wavelength of the signal. This range of maximum body absorption is known as the resonant frequency range, which occurs roughly between 30 MHz and 300 MHz.
Of the frequencies listed, 50 MHz (the 6-meter band) falls directly into this region where the human body absorbs the most energy. Therefore, the FCC’s MPE limit is lowest (most restrictive) in this range, requiring more stringent precautions regarding power and distance.
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