Specific Absorption Rate (SAR) is an electromagnetic measurement of radio frequency that occurs when using electronic devices (mobile phones, computers, microwave ovens, etc.) in daily life. SAR is the tests that measure the expressed of watts per kilogram (W/kg) or milliwatts per gram (mW/g) and measure the absorbed by the human body or animal when using electronics devise. it can also refer to absorption of other forms of energy by tissue, including ultrasound.
When a human body is exposed to electromagnetic waves with a low frequency (low frequency, 1 Hz to 100 kHz), this stimulates the nerve (stimulating action) due to the current induced in the human body, and if the human body is exposed to high frequency electromagnetic waves, (high frequency, 100㎑ ~ 10㎓), the thermal action that increases body temperature will occur. Electromagnetic Absorption from mobile phones can cause the increasing temperature for human body as high frequencies, and SAR is the quantitative expression of such thermal action.