Today, I was doing the experiment on half-wave rectifiers with my batchmates, in the Device Characterization lab. At one point, I switched on the CRO for checking the output. I had fixed the probe onto the CRO, and was casually holding one of the the open terminals, trying to find where on the cluttered breadboard I was supposed to fix them, when I noticed a clean sine wave displayed on the CRO. I looked at the terminals of the probe, but I was holding one of them, and the other was dangling freely in midair. When I took my hands off, the wave disapeared! How did the sine wave appear out of thin air? Funny that that’s exactly how it appeared – out of thin air! Surrounding me was a number of hidden wires carrying a 230V, 50Hz sine wave. Electromagnetic waves produced by the large alternating voltage induced a corresponding wave in the terminals of the CRO probe which were acting like an antenna (because of the completion of some circuit on my touch).
We are surrounded by electromagnetic radiations of different kinds. Some we can feel and perceive, like the visible radiations, and the infrared(heat). But these waves are not very strong when they reach us. On the other hand, there is a spectrum of manmade electromagnetic radiations, like radio waves, satellite signals, mobile phone signals etc. which are quite strong as they have to travel only a small distance, and make wireless communication possible. These waves are always around us. We are literally lost in the “electromagnetic jungle”! These waves radiate a significant amount of electromagnetic energy, which interacts with our body whose nervous system works on electomagnetic signals as well, albeit of a different kind. In the long run, no one can really guess how prolonged exposure to these strong manmade signals can interfere with and deform our nervous system.
It is known that people living very near to the high power transmission lines are prone to diseases like cancer. Though in this case, the varying voltages are of the order of kilovolts (which is huge), it is only 50 Hz. Power radiated by an electromagnetic wave increases with frequency, for a fixed voltage. So the waves produced by our cell phone, which might be only a couple of volts or less, but which have frequencies of giga Hz or more, can be equally harmful in the long run. Especially our generation, which has been exposed to these waves right from birth.