Which of the following statements about RF exposure is true?

The statement regarding RF exposure that is true indicates that limits for exposure are indeed based on both frequency and power density. This understanding is rooted in the way radio frequency (RF) energy interacts with biological tissues. Different frequencies can penetrate tissues to varying extents and have different thermal effects, while power density refers to the amount of power that is transferred per unit area.

Regulatory bodies such as the Federal Communications Commission (FCC) and the Institute of Electrical and Electronics Engineers (IEEE) have established guidelines and safety standards based on these factors. These limits aim to protect individuals from potential harm caused by excessive exposure to RF energy.

Understanding the importance of frequency and power density is crucial, as it guides safe practices in both amateur radio and commercial RF applications. Thus, the correct option meaningfully reflects the scientific principles underlying RF exposure safety protocols, making it essential knowledge for anyone involved in operating or working around RF equipment.