by happyphysicsman on Fri Feb 12, 2010 9:03 am
The burning at radio-frequency has more to do with the frequency band that our bodies resonate at. For example, you already mention magnetic-resonance imaging. In MRI, there are two pieces of equipment that are involved in the imaging process: The high powered magnetic coil, and the RF modulators that are "straped" to you. The ONLY medical concern, (As MR is extremely safe as long as there is no ferromagnetic material in the magnetic field - watch out if there is) is the SAR: specific absorption rate which they keep under careful watch and is highly regulated by government and medical agencies.
That is: the RF frequency has the potential to induce a small electric current in tissue. This electric current is quickly absorbed in the body and reveals itself as radiation dose to the tissue or a burn. In MR, there have been literally less than a handful of patients who have experiences any effects from SAR overdose since the effect is extremely low.
On the other hand, technicians for cell towers or radio frequency transmitters have to pay careful attention to their SAR as they service the tower equipment since the magnitude of waves and their energy is so great they will experience burns to their skin from over exposure.
The effect with oncology radiation is completely different. Here we place patient's cancer in the direct beam of high powered radiation which delivers a dose directly to the patient's tissue. With RF, the radiation induces and small current within the tissue which subsequently delivers the dose, thereby the RF has more of an indirect effect on human tissue.
With Cell phone, the magnitude of the signal is so low, there is a negligible effect on the human tissue. The probability of any sort tissue toxicity (what we call any undesirable effect to tissue from radiation) is extremely low...EXTREMELY LOW -> practically non-existent. I don't know of any case when a human was burned from cell phone use. Around the cell towers, its a different story since within 10 meters of the tower, the intensity is so massive, one must take precautions.
ON the question of whether or not there is an upper-bound to the frequency of electromagnetic radiation. No, I don't believe so, but we have never observed anything more energetic than few GeV's.
It is important that we make the distinction between photon, the carrier particle of electromagnetic radiation which are massless, and all other particles that have mass. There is no other quantum constituent to the photon. It has no mass, and no size and is purely an elemental particle. All other atomic particles: protons, electrons (maybe), neutrons, pions and such are made out of other purely elemental particles. We have found some, and are looking for others. Metronid pointed out that you would need large enough energies to brake the binding properties, thus the building of large, overly expensive (on the order of Billions and billions of dollars), accelerators that will collide particles braking them in pieces and seeing what is produced. Sometimes, from the large amount of energy involved, chucks of that energy is converted to larger more massive particles.
The large Hadron Collider, the most powerful, technologically advanced, expensive, and largest accelerator was built primarily to produce one such massive particle called the Higgs Boson: the super particle that will prove to be the particle that will join some foundational theories into some Grand Unified theory. I really don't know much about that as that is all high energy particle physics and way outside my relm.
My expertise is in what's referred to as computational physics. I write computer programs that solve mathematically intensive physics problems that are way too complex to do on paper. My current research, as a PhD graduate student, is centered around precise, accurate, and patient specific dose calculation for a form of radiotherapy that involved the intensive procedure of implanted small (about the size of a grain of rice) radioactive sources into the tumor bed. Usually about 60-100 sources can be used. It is a very complex problem to solve, so we write computer simulations to do it for us as we simulate the physical interactions of the radiation in the patient. Much easier way to do it.
HPM
'05 Met II in process of becoming a Met I