Skin Heating Effects frequency range?

Skin Heating Effects frequency range?

• A. 100 kHz-3 GHz
• B. 3 kHz-5 MHz
• C. 3 Hz-3 kHz
• D. 3 GHz-300 GHz

Answer: (D)

As frequency increases, electromagnetic energy is absorbed more and more near the surface of the skin because the skin depth gets smaller. Skin depth is roughly δ ≈ sqrt(2/(ω μ σ)), where ω = 2πf, μ is tissue permeability, and σ is electrical conductivity. When f rises, δ shrinks, so most of the energy is deposited in a very thin surface layer. That surface-focused absorption is what we call skin heating. This makes the microwave to millimeter-wave range the one where skin heating is the dominant thermal effect—roughly from a few gigahertz up to a few hundred gigahertz. In the lower frequency bands, energy penetrates deeper into the body, producing heating that isn’t confined to the surface and is governed by different exposure characteristics.

As frequency increases, electromagnetic energy is absorbed more and more near the surface of the skin because the skin depth gets smaller. Skin depth is roughly δ ≈ sqrt(2/(ω μ σ)), where ω = 2πf, μ is tissue permeability, and σ is electrical conductivity. When f rises, δ shrinks, so most of the energy is deposited in a very thin surface layer. That surface-focused absorption is what we call skin heating.

This makes the microwave to millimeter-wave range the one where skin heating is the dominant thermal effect—roughly from a few gigahertz up to a few hundred gigahertz. In the lower frequency bands, energy penetrates deeper into the body, producing heating that isn’t confined to the surface and is governed by different exposure characteristics.