We all just carved pumpkins not too long ago. We can use pumpkins to explain one of these questions. If you put a 5 watt light bulb at the center of your carved pumpkin, then each square inch of the internal pumpkin surface gets the amount of light energy given by the expression:
5W / (internal surface area of pumpkin) = light energy per square inch Now you move your light bulb to a bigger pumpkin and do the same calculation. You find that each square inch of your bigger pumpkin gets less light energy due to a bigger surface area. This is why RF signals drop off at the rate of 1/distance squared, since the pumpkin surface area is proportional to the square of the radius. Light is simply a higher frequency emission than RF, but the same concept applies. As far as "How RF travel through vacuum," you can think of it this way: RF is composed of electric field and magnetic field. Electric field is simply the attraction force between the positive charges and the negative charges. And magnetic field is the interaction between 2 current loops. It is not hard to imagine that refrigerator magnets will work in vacuum or protons and electrons will attract in outer space. RF is simply the electric and magnetic fields changing polarity at a very rapid rate. George -----Original Message----- From: brian_kunde [mailto:brian_ku...@leco.com] Sent: Thursday, November 30, 2000 12:51 PM To: emc-pstc Subject: How does RF travel through outer space? Hello, I'm sorry if this is too simple of question... "How does RF travel through outer space?". I will be teaching a class in which this question will come up. I want to be prepared with all the basic science behind this principal. I need an explaination that is simple and easy to understand. People seem to have no problem understanding how waves can travel through mass such as a body of water but can not understand how it can travel where there is no mass. I also understand that there is a lot of debate over how Light travels through space (photons and all). Also, I understand that RF signals degrade at a rate of 1/distance(squared). What force is causing this attenuation? Try to keep it simple for my audience it not all that technical. Appreciate the help. Please forgive any improper punctuation or word misuse. Brian ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
