ELECTROMAGNETIC WAVES

Who is Cristiano Ronaldo? Or, who is vocalist Peter Pan? If you're faced with such questions can be sure you can answer it, right? Who does not know CR7 (Cristiano Ronaldo for the title) or Ariel Peter Pan? Although you never meet directly with them, you must be familiar with them, right? How could you! Although you never meet them you'll often see them on TV, right? Now, what makes you able to watch TV to see a football match going on in other places very far away? Do you know what principles and concepts underlying the technology and the phenomenon? 

He was so small that can be comfortably placed in the pocket, but is considered to have a very large function primarily to communicate. Yes, it is a mobile phone (cell phone). Nowadays mobile phones are not only used for phoning, but also for other functions such as send and receive short messages (SMS), listen to music, or taking photos. How mobile devices can connect with other mobile devices when they are far from each other?
The concept that could explain this phenomenon is the concept of electromagnetic waves. And, the concept was very broad electromagnetic waves is not only associated with TV or cell phone only, but many other applications that can often be found daily around us. Applications include microwave, radio, radar, or x-ray.
As previously discussed that there are two basic laws of electricity and magnetism connected symptoms. 

First, the electrical current can generate (induce) the magnetic field. This phenomenon is known as magnetic induction. Foundation stone of this concept is the Oersted had discovered this phenomenon experimentally and formulated in full by Ampere. Symptoms of magnetic induction is known as Ampere's Law.

Second, the magnetic field varies with time can generate (induce) electric fields in the form of electrical current. This phenomenon is known as electromagnetic induction phenomenon. The concept of electromagnetic induction discovered by Michael Faraday experimentally and formulated in full by Joseph Henry. Electromagnetic induction law itself became known as the Faraday-Henry Law. 

From these two basic principles of electric magnets above and taking into account the prevailing concept of symmetry in the laws of nature, James Clerk Maxwell submitted a proposal. Maxwell proposals put forward, namely that if the magnetic field time-varying electric fields can produce the opposite may be happening. Thus Maxwell suggested that the electric field that changes with time can generate (induce) the magnetic field. Maxwell's proposal was later to become the third law that links between electricity and magnetism.


Thus, the third principle is the electric field varies with time can produce a magnetic field. The third principle is expressed by Maxwell is basically a development of the formulation of Ampere's law. Therefore, this principle is known as the Ampere-Maxwell Law. 

Of the three basic principles of electricity and magnetism at the top, Maxwell saw an archetype. Magnetic field can generate a time-varying electric field is also changing with time, and the electric field change with time can also generate a magnetic field. If this process is continuous it will produce a magnetic field and electric field are continuous. If the magnetic field and electric field was simultaneously propagate (spread) in all directions in space then this is a wave phenomenon. Such waves are called electromagnetic waves because it consists of electric and magnetic fields that propagate in space.