Question
Why do exposure limits vary with frequency?
Answer Options
- A) Lower frequency RF fields have more energy than higher frequency fields
- B) Lower frequency RF fields do not penetrate the human body
- C) Higher frequency RF fields are transient in nature
- D) The human body absorbs more RF energy at some frequencies than at others
Correct Answer: D
Explanation
The maximum permissible exposure (MPE) limits are not uniform across all radio frequencies because the human body is not uniform in its ability to absorb RF energy across the spectrum. As noted in T0C02, the body acts as an antenna.
The MPE limits vary because the human body absorbs more RF energy at some frequencies than at others. At the body’s resonant frequency range (around 30 MHz to 300 MHz), absorption is highest, requiring the strictest (lowest) exposure limits to prevent the average absorbed energy from exceeding safe thresholds.
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