*Question T0C02:
At which of the following frequencies does maximum permissible exposure have the lowest value?*  

*Correct Answer is  B: 50 MHz*  

### AI Response: (may contain errors)  

To determine at which frequency the maximum permissible exposure (MPE) has the lowest value, we need to understand how MPE varies with frequency.

1. **Correct Answer: 50 MHz**
   - The MPE is lowest at 50 MHz because, according to the Federal Communications Commission (FCC) guidelines, the MPE limits for radiofrequency (RF) exposure are frequency-dependent. As frequency increases, the MPE values generally increase as well. At 50 MHz, the MPE is lower compared to higher frequencies like 440 MHz and 1296 MHz.

2. **Why the Other Choices are Incorrect:**
   - **3.5 MHz:** This frequency is lower than 50 MHz, and the MPE values are higher than at 50 MHz. Lower frequencies typically have higher MPE limits.
   - **440 MHz:** This frequency is higher than 50 MHz, and the MPE values are higher as well. The exposure limits increase with frequency.
   - **1296 MHz:** This is the highest frequency among the choices, and it has the highest MPE limits. As frequency increases, the MPE continues to rise.

3. **Useful Rules of Thumb:**
   - MPE limits are defined in terms of power density (watts per square meter) and are frequency-dependent.
   - Generally, as frequency increases, the MPE limits also increase, meaning that the exposure limits become less stringent at higher frequencies.

In summary, the correct answer is 50 MHz because it has the lowest MPE value compared to the other frequencies listed.