Specific absorption rate - with Electric intensity


Specific absorption rate (SAR) is a measure of the rate at which energy is absorbed by the human body when exposed to a radio frequency (RF) electromagnetic field; although, it can also refer to absorption of other forms of energy by tissue, including ultrasound.t is defined as the power absorbed per mass of tissue and has units of watts per kilogram (W/kg).

SAR is usually averaged either over the whole body, or over a small sample volume (typically 1 g or 10 g of tissue). The value cited is then the maximum level measured in the body part studied over the stated volume or mass.

SAR for electromagnetic energy can be calculated from the electric field within the tissue as shown.

SAR measures exposure to fields between 100 kHz and 10 GHz (known as radio waves). It is commonly used to measure power absorbed from mobile phones and during MRI scans. The value will depend heavily on the geometry of the part of the body that is exposed to the RF energy, and on the exact location and geometry of the RF source. Thus tests must be made with each specific source, such as a mobile phone model, and at the intended position of use.

Related formulas


SARspecific absorption rate (W/kg)
σsample electrical conductivity (S/m)
ERMS electric field (V/m)
ρsample density (kg/m3)