How electromagnetic waves works, how they are created and how thay transform to electric signal? [closed]

Few days I am trying to learn more about electromagnetic waves, induction, electromagnetic spectrum... And how it's connected.

Here is what I understand now:

There is a lot of electromagnetic waves depend on their wavelength and frequency:

-infrared waves
-visible
-microwaves


Electromagnetic wave is produced when we have oscillating electric and magnetic fields.

an oscillating electric field generates an oscillating magnetic field, and reverse.

First group of questions:

If we have oscillating electric or oscillating magnetic fields, dose it will create electromagnetic wave?

Could you on some simple example show me how is electromagnetic wave produced?

Also how we can know which wave will be created from electromagnetic spectrum?

Second group of question is about radio waves on example of wi-fi:

Also how that radio wave with data will transform to electrical signal and latter appear on our monitors?

closed as too broad by Olin Lathrop, Andy aka, Leon Heller, Brian Drummond, PeterJDec 6 '15 at 22:24

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• The scope of the question may seem simple but the answers could fill a shelf of a library hence the question will likely be closed because of it's broadness. Try studying mawell's equations. – Andy aka Dec 6 '15 at 15:14
• so much questions! – AHB Dec 6 '15 at 15:45
• Andy aka those who really understand can explain it simply. – Vladimir Dec 6 '15 at 16:08
• @Vladimir how would you know that given that you are asking the question? – Andy aka Dec 6 '15 at 17:38
• Radio waves carry data (or analog signals) using some form of modulation. Signals are converted to radio waves using antennas. Radio waves are converted to electrical signals using antennas also. Wifi uses a modulation scheme which is kind of difficult to explain, but it does also use antennas. The information contained in wifi is converted to digital data and sent to your computing device. Computer programs determine what to do with the data. If the data is a video, the program decodes the data and paints images on your screen. – mkeith Dec 6 '15 at 21:02

As you say, "those who really understand can explain it simply." However, the answers that can fit here will only be simplifications of the full explanation and will raise more questions than they answer.

Here, I'll show you:

If we have oscillating electric or oscillating magnetic fields, dose it will create electromagnetic wave?

Yes.

Could you on some simple example show me how is electromagnetic wave produced?

Connect an oscillating voltage source to an antenna. An EM wave will be produced.

Also how we can know which wave will be created from electromagnetic spectrum?

The frequency will be the same as the oscillating frequency of whatever source produced it.

The strength and direction will depend on the geometry of the antenna that emitted it.

Some aspect of the signal (amplitude or phase or both) is modulated.

Also how that radio wave with data will transform to electrical signal and latter appear on our monitors?

The signal is demodulated at the receiver to recover the data. How it is displayed on your monitor depends on the configuration of the hardware and software you are using to present the received data on the monitor.

The full answers to your questions would fill several university courses. In particular, how EM waves are produced, how signals are modulated to carry data, and how data can be decoded and presented on a monitor are usually treated as entirely separate topics and taught in entirely separate courses in university.

• You are definitely very good with this. I know this is big matter but for beginning I will need just to understand concept and how things work. Last question is still unclear for me, so I have one more: When anthena of receiver take EM wave how that wave is transformed to electrical signal or what turn EM wave to electrical signal? Also is there any good sorces for that courses on the internet? And thanks, I apricate your help! – Vladimir Dec 6 '15 at 23:18
• There are different types of antennas. Here is an explanation of a simple one. Radiation traveling through space as a time varying electromagnetic field encounters a conductive rod. The electric field causes current to flow in the conductive rod. Why? That is a basic law of physics. Whenever mobile charges are exposed to an electric field, they will start to flow along the electric field. The antenna just has to be designed so that the charge flow can be detected and decoded. – mkeith Dec 6 '15 at 23:34
• Is that work on pricncip electromagnet induction? like on this video look at 1:05 min: youtube.com/watch?v=RZVGZ-6W05Y ? – Vladimir Dec 7 '15 at 11:30
• @Vladimir, no, what mkeith described is coupling through the electric field. Induction devices work by coupling through the magnetic field. An antenna that works through magnetic coupling would be a loop antenna. But we still wouldn't normally call that "induction" because "induction" usually implies a near-field phenomenon, whereas an antenna will be designed for use in the far field (far enough from the transmitting antenna that the EM waves can be accurately modeled as plane waves). – The Photon Dec 7 '15 at 16:42
• See Peter's answer. – The Photon Dec 7 '15 at 18:02

$$\nabla \cdot \mathbf{E} = \frac {\rho} {\varepsilon_0}$$
$$\nabla \cdot \mathbf{B} = 0$$
$$\nabla \times \mathbf{E} = -\frac{\partial \mathbf{B}} {\partial t}$$
$$\nabla \times \mathbf{B} = \mu_0\left(\mathbf{J} + \varepsilon_0 \frac{\partial \mathbf{E}} {\partial t} \right)$$