Why is there an interval between lightning and thunder?

The reason for this is that light travels faster than sound. The speed of light is 300,000Km per second. 

on the contrary, sound is slow and covers only about 330m in one second, I.e.,one kilometre in 3 seconds. If we count the seconds till we hear  the thuder of the seeing the flash of lightning in the sky and divide this  value by three, we will know how many kilometers the  storm is away from us. Lightning bolts up the surrounding air all  of a sudden  as a result thuder occurs..