At which of the following frequencies does maximum permissible exposure have the lowest value?
3.5 MHz
Incorrect, because, at 3.5 MHz (within HF band), the body absorbs less RF energy compared to 50 MHz, resulting in higher permissible exposure limits.
50 MHz
Correct, because 50 MHz falls within a frequency range where the human body absorbs RF energy more efficiently, leading to lower MPE values to prevent excessive exposure.
440 MHz
Incorrect, because, at 440 MHz (UHF band), although the body absorbs significant RF energy, it is not as efficient as at 50 MHz, resulting in relatively higher permissible exposure limits.
1296 MHz
Incorrect, because, at 1296 MHz (microwave range), the body absorbs RF energy differently compared to 50 MHz, resulting in higher permissible exposure limits.
Explanation
Understanding Frequency Limits for Maximum Permissible Exposure (MPE) is vital for ensuring safe operation in amateur radio. The FCC establishes MPE limits to protect both the general public and amateur radio operators from excessive radio frequency (RF) exposure. The MPE varies with frequency because the human body absorbs RF energy differently at different frequencies. The frequency of 50 MHz corresponds to the VHF (Very High Frequency) range, a range where RF energy is absorbed more efficiently by human tissues. As a result, the MPE for 50 MHz is set to a lower value compared to other frequencies, indicating that less power is required to exceed safe exposure limits. Understanding these exposure limits helps ensure that amateur radio operators set up their equipment safely, minimizing potential health risks from prolonged exposure to RF energy.
T0C02 2022-2026