The Physics
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Power of a Cell Phone Transmitter

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Levi, Anthony. Applied Quantum Mechanics. Cambridge: Cambridge University Press, 2003: 66. "This particular cell phone operates at a center frequency ν0 = 1 GHz, and the radiated power is P0 = 300 mW." 0.3 W
Muller, Nathan J. Wireless A to Z. New York: McGraw-Hill, 2003: 39. "Powerful 3-watt telephones are typically of the vehicle-mounted or transportable type." 3 W
Vecchione, Glen. Blue Ribbon Science Fair Projects. Toronto: Starling Publishing, 2005: 64. "Although most car phones have a transmitter power of 3 watts, a handheld cell phone operates on about 0.75 to 1 watt of power." 0.75 to 1 W
Kaplan, Laura G. Emergency and Disaster Planning Manual. Boston, MA: McGraw-Hill, 1996: 204. "By using the high-power version of cellular phones (the bag phone is 3 watts)…" 3 W
Layton, Julia, Marshall Brain and Jeff Tyson. How Cell Phones Work. Miami: HowStuffWorks, 1998-2006. "Many cell phones have two signal strengths: 0.6 watts and 3 watts (for comparison, most CB radios transmit at 4 watts)." 0.6 to 3 W

Among the common warnings of be sure to put on SPF before going out in the sun  and you shouldn't have too many or even any x-rays , another equally known warning also exists. However, this one only affects 1.5 billion people in the world. What sets them apart from the rest of the global population is that they are all cell phone users and are thus prone to direct radiation to their head tissue.

The transmitter, which is an electronic device in the cell phone located near the antenna, is where a carrier wave is produced and amplified. It is here, too, that the carrier wave (specifically a radio wave made up of electromagnetic radiation) is then modulated with a signal coming from a source such as speech. The resulting signal that emerges from this process is then propagated through the antenna. This, in turn, is how having a cell phone against the ear exposes the cell phone user to radiation.

Meanwhile, the total power emitted from the cell phone itself ranges from 0.75 to 1 watt. According to the FCC (Federal Communications Commission), this is an acceptably safe amount of power for a cell phone since their cut-off or specific absorption rate  is only 1.6 watts per kilogram (W/kg). As a result, the power radiated from a cell phone is considered as non-ionizing as opposed to ionizing. This means that it is safe and causes only a bit of heating as opposed to having enough electromagnetic energy to take apart the makeup of body tissue and trigger chemical reactions like x-rays do. Even so, the long-term effects of cell phone radiation are still not known so its best to just avoid the risks by checking the label the next time you purchase one.

Ebru Bek -- 2006