A charge kept at one location is modifying space somewhere else,

• Waves are easy to understand. Get a bunch of particles, make sure they have some force of attraction among themselves, and then disturb one particle, and it will disturb the others and so the disturbance propagates through the medium, A.K.A mechanical wave.

Using this concept, how do we visualize or even conceptualize a wave that could travel in vacuum? Impossible isn’t it? That’s what many people had though. People thought it was so impossible that they strongly believed that there must be a medium that exists throughout vacuum. But eventually we found out, that there wasn’t any medium through out space. So light was truly travelling in vacuum without any medium and it was proved to be a wave.

• The secret lies in the four Maxwell equations. The equations of electricity and magnetism. The equations that changed the way we looked at the world and gave way to the technological revolution of the 19th and the early 20th century.
• So to understand these light waves fully, one needs to undergo a course in electricity in magnetism. But to just get a feeling of how these waves propagate in vacuum of space, you just need to understand what electric and magnetic fields are. [No not the way in which your textbooks and teachers teach you, but in a little different way, a way in which you can see how radical the ideas are]
• Electric and Magnetic fields summary: Since charged particles can attract and repel each other from a distance, we believe that every charged particle the surrounding space. If you keep a positive charge at (0,0), then the T space. This is a radical theory developed mainly by Micheal Faraday. A charge kept at one location modifying space somewhere else. Isn’t that wonderful? I can keep dwelling on this concept for hours together. Just like how a charge creates an electric field which pushes and pulls other charges, a moving charge creates yet another kind of ‘modification of space’ that pulls and pushes other moving charges. This is what we call as magnetic field. [A foot note, one of the great victories of Einstein’s theories is that, he proved that these electric and magnetic fields are basically the same things looked from different perspectives, but lets not worry too much about them, we will consider them to be two separate ‘modifications’ of space results from and affecting two separate things – static charges and moving charges]
• So this concept had become pretty famous throughout the mid-19th century. The idea of charge creates electric fields and if these charges are moving, they create an additional magnetic field. But Faraday and Maxwell found out that you could create these fields without charges at all. They found out a changing electric field can produce a magnetic field and vice versa. And this is the key to understanding electromagnetic waves. End of Electric and Magnetic fields summary
• How EM waves propagate in space: Now lets consider an empty universe with no charges, fields, or whatever. Consider two points, A and B separated by 300 km. Obviously, nothing exists at these two points, no charges, no fields. Now Suppose magically, at t=0 a positive charge pops in at A. [I know you can’t do this in reality, but you can understand EM waves this way easily]. Here is the question, is there an electric field at B at t=0? The answer is No. The space at point B doesn’t even know that a charge has appeared at point A. And so does every point in space. Everywhere the field is zero. But let’s go in the vicinity of the charge at A. Let’s go very close to it, very close, very very very close, so close that we are almost at A. But not at A. But infinitesimally close to it. Since this distance is a differential distance, at t=0 exists a non-zero electric field at this point. But wait, the electric field was zero, before the charge popped in. But now it’s changed. And I told you, a changing electric field creates a magnetic field in its vicinity. So, as time passes by, a magnetic field is generated at the vicinity. But wait, there was no magnetic field to begin with at this point, so the magnetic field has changed. This generates an electric field in it’s vicinity. This is how new electric fields and new magnetic fields are generated slowly and steadily at every point farther and farther away from the charge. At about t= 1 ms, the electric field gets generated at point B, and keeps moving on from here.
• These changes in electric and magnetic fields, or put in other words, changes in the modifications of space, is what keeps creating new modifications in the space near by. This is an electromagnetic wave.
• Fascinating, isn’t it? It’s unlike any other wave at all. Since charges are affected by these modifications of space, they are affected by EM waves. If such an EM wave were to get focused in the retina of your eye, it would make the electrons of the retina cell react to it, making it oscillated with the frequency of the EM waves. This would create an electric current which runs up the optic nerves all the way to the parts of the brain, which results in some chemical reactions which finally cause the sensation of sight.