Cell-phone Radiation

Just by their basic operation, cell phones have to emit
a small amount of electromagnetic radiation. If you've read
How Cell Phones Work, then you know that cell phones emit
signals via radio waves, which are comprised of
radio-frequency (RF) energy, a form of electromagnetic
radiation.

There's a lot of talk in the news these days about whether or
not cell phones emit enough radiation to cause adverse health
effects. The concern is that cell phones are often placed
close to or against the head during use, which puts the
radiation in direct contact with the tissue in the head.
There's evidence supporting both sides of the argument.

Source of Radiation

When talking on a cell phone, a transmitter takes the sound
of your voice and encodes it onto a continuous sine wave. A
sine wave is just a type of continuously varying wave that
radiates out from the antenna and fluctuates evenly through
space. Sine waves are measured in terms of frequency, which
is the number of times a wave oscillates up and down per
second. Once the encoded sound has been placed on the sine
wave, the transmitter sends the signal to the antenna, which
then sends the signal out.

Cell phones have low-power transmitters in them. Most car
phones have a transmitter power of 3 watts. A handheld cell
phone operates on about 0.75 to 1 watt of power. The position
of a transmitter inside a phone varies depending on the
manufacturer, but it is usually in close proximity to the
phone's antenna. The radio waves that send the encoded signal
are made up of electromagnetic radiation propagated by the
antenna. The function of an antenna in any radio transmitter
is to launch the radio waves into space; in the case of cell
phones, these waves are picked up by a receiver in the
cell-phone tower.

Electromagnetic radiation is made up of waves of electric and
magnetic energy moving at the speed of light, according to
the Federal Communications Commission (FCC). All
electromagnetic energy falls somewhere on the electromagnetic
spectrum, which ranges from extremely low frequency (ELF)
radiation to X-rays and gamma rays. Later, you will learn
how these levels of radiation affect biological tissue.

When talking on a cell phone, most users place the phone
against the head. In this position, there is a good chance
that some of the radiation will be absorbed by human tissue.
In the next section, we will look at why some scientists
believe that cell phones are harmful, and you'll find out
what effects these ubiquitous devices may have.