At which of the following frequencies does maximum permissible exposure have the lowest value?

The maximum permissible exposure (MPE) levels differ across frequencies due to various biological effects that radiofrequency (RF) radiation can have on the human body. As frequency increases, there are specific thresholds set that determine safe exposure levels based on the potential for thermal effects.

In the range of frequencies given in the question, the lower frequencies, such as 3.5 MHz, are generally associated with larger wavelengths that do not penetrate as deeply into body tissue. As we move to higher frequencies, specifically in the range of 50 MHz up to 1296 MHz, the MPE values tend to become more restrictive because these frequencies can cause greater heating effects in biological tissues.

In this context, the frequency of 50 MHz has a lower MPE value compared to the others listed because it is still capable of penetrating the body to a certain degree, thus necessitating stricter limits to ensure safety from possible adverse health effects. As the frequencies increase, the potential for exposure that could lead to harmful thermal effects also increases, prompting the regulations to adjust the permissible limits accordingly.

Therefore, while 440 MHz and 1296 MHz might have higher exposure limits, 50 MHz represents a critical threshold as the first frequency that starts to require a more significant reduction