*Question G0A07:
What is the effect of modulation duty cycle on RF exposure?*  

*Correct Answer is  A: A lower duty cycle permits greater power levels to be transmitted*  

### AI Response: (may contain errors)  

The correct answer is: A lower duty cycle permits greater power levels to be transmitted.

1. **Why the correct answer is correct:**

   - **Duty Cycle**: The duty cycle is the fraction of time a transmitter is actively transmitting a signal. It is expressed as a percentage or a ratio.
   - **RF Exposure**: The exposure to radio frequency (RF) energy is averaged over time. A lower duty cycle means the transmitter is on for a smaller fraction of the time, reducing the average RF exposure.
   - **Power Levels**: Because the average exposure is lower with a lower duty cycle, higher peak power levels can be used without exceeding safe exposure limits.

2. **Why the other choices are incorrect:**

   - **B: A higher duty cycle permits greater power levels to be transmitted**  
     This is incorrect because a higher duty cycle means the transmitter is on more often, increasing the average RF exposure. This limits the allowable peak power to stay within safe exposure limits.

   - **C: Low duty cycle transmitters are exempt from RF exposure evaluation requirements**  
     This is incorrect because all transmitters, regardless of duty cycle, must be evaluated for RF exposure. The duty cycle affects the allowable power levels but does not exempt a transmitter from evaluation.

   - **D: High duty cycle transmitters are exempt from RF exposure requirements**  
     This is incorrect because high duty cycle transmitters typically require more stringent evaluation due to higher average RF exposure.

3. **Useful Formula:**

   - **Average Power Calculation**:  
     $$ P_{\text{avg}} = P_{\text{peak}} \times \text{Duty Cycle} $$
     - $P_{\text{avg}}$: Average power over time
     - $P_{\text{peak}}$: Peak power during transmission
     - Duty Cycle: Fraction of time the transmitter is active

   This formula shows how the duty cycle affects the average power, which is crucial for RF exposure evaluations. A lower duty cycle reduces $P_{\text{avg}}$, allowing for higher $P_{\text{peak}}$.