Does anybody of you know what electromagnetic waves are?

Click start to see how light waves propagate in empty space

Sir,I can't tell you what are electromagnetic waves but I do know about waves like water waves that get generated when we drop a stone into water.Well,I have heard that the sound we speak and the light are also waves.

Waves are disturbances that repeat themselves.

Right ,both of you have made valid points but Rohina you talked about two kind of waves(actually 3 water, sound&light wave).Can you tell me how are they different? Well, that is  a difficult question. I therefore give you a hint and whoever tells me the right answer would get a chocolate. Light is something that we get from sun which comes to us after traveling thousands and thousands of miles whereas look at sound or water waves the way they travel.

Sir,I got it. Light is a faster wave as compared to sound or water waves.

Sir,light travels without medium (there is nothing between sun and earth) while the other two travel in mediums, sound in air water wave in water.

Oh, thats not true light comes to earth and on earth it travels through air.I got the choclate sir.

Well,Rahul both of you were correct but let me tell you the last point you made is not true.I don't mean to say you won't get the chocolate but that light may seem to go through air but that does not mean it requires air for its propagation.If it had then how could it have come to us from sun as Rohina pointed out?.

Now, let me tell you what actually electromagnetic waves are.They are disturbances like sound or water waves but the important point is that they don't require medium.Now what exactly does that mean? It means look at sound wave. When you speak the air particles near your mouth get disturbed which in turn disturb the nearby air particles and this disturbance goes on propagating until it reaches the eardrum in your ear and you get the sensation of sound.So no air would have meant no disturbance and therefore no propagation. Hence medium is necessary for the propagation of such waves(called mechanical waves).Now lets look at light wave.Unlike the previous wave lightwave consist of mutually perpendicular electric and magnetic field oscillating in free space and the propagation of these varying fields in space is what we term as ELECTROMAGNETIC waves.This is what you can see in above demo clearly.

Now I got it sir but there is another difference which I can observe.Light waves travel perpendicular to the direction of propagation whereas in case of sound it travels in the same direction in which the air particles oscillate.

That's a excellent poin Rahul. In fact you have hit upon the concept of transverse and longitudinal wave.Let me tell you a deeper thing.All these waves,I mean any wave that you can think of have some parameter that varies like pressure(or displacement) of air particle in a region for sound waves,electric or magnetic fields in case of light waves and displacement of water particles in case of water waves.In higher classes you would study about matter waves and there the probablity to find the matter varies.If the direction in which parameter varies is normal to the direction of propagation the wave is called transverse and if they are in same direction they are called longitudinal.