Suppose we have a stretched string, with one of its end fixed at a wall. Now if we just jerk the string(up and down), we get a mechanical wave, i.e. the disturbance caused by us at one end of the string travels to the other end. Now the question is, how and why does the disturbance travel through the string. All we do is just jerk the end of the string up and down, so what makes that disturbance travel along the string(perpendicular to the direction of the force we apply). And now I would like to extend this to the electromagnetic waves. EM radiation consists of electric and magnetic oscillations. But how and why do these oscillations travel forward.