some useful kownledge about RF Radiation and Electromagnetic Field Safety

Body tissues that are subjected to very
high levels of RF energy may suffer serious
heat damage. These effects depend on
the frequency of the energy, the power
density of the RF field that strikes the body
and factors such as the polarization of the
wave.
At frequencies near the body’s natural
resonant frequency, RF energy is absorbed
more efficiently, and an increase in heating
occurs. In adults, this frequency usually
is about 35 MHz if the person is
grounded, and about 70 MHz if insulated
from the ground. Individual body parts
may be resonant at different frequencies.
The adult head, for example, is resonant
around 400 MHz, while a baby’s smaller
head resonates near 700 MHz. Body size
thus determines the frequency at which
most RF energy is absorbed. As the frequency
is moved farther from resonance,
less RF heating generally occurs. Specific
absorption rate (SAR) is a term that describes
the rate at which RF energy is absorbed
in tissue.