Lightning and Thunder formtion

Lightning and Thunder

                      We know that the velocity of light is 3 multiply 10 to the pow of 8 m/s. It means that the light can travel a distance 3 multiply 10 to the pow of 8 metre in one second.

             The velocity of sound in air at 20degeree celcious is nearly equal to 340 m/s. Hence sound can travel a distance 340 metre in one second.

             Through the lightning and the thunder take place at the same time, due to difference in the velocities of the light and the sound, lightning can be seen early and later the thunder sound is heard.  

Lightning formation:

 Lightning is an electrical discharge through the atmosphere due to the charges accumulated on the clouds. the atmospheric air is continuously ionised  by the action of the ultraviolet rays from the sun and the cosmic rays. As a result, the atmospere always contains positive and negative ions. when the water droplets of the cloud fall through this electric field region, they get charged.       

                 According to C.T.R wilson, the heavier droplets acquire negative charges and the lighter droplets acquire positive charges. this leads to the clustering of negative charges at the base of the cloud and the positive charges at the top.

                  A discharge takes place between the charged surfaces of the same cloud or between two clouds when they pass one over the other. The flash produced by the discharge is called the 'lightnig'.

Thunder formation:

                  About 75% of the electrical energy of the lightning discharge is used up in heating the atmospheric gases in and around the flash.

                     The temperature of this region rises to about 10000 K in about a few microsecond. As a result, a pressure wave, on expansion, gives rise to compressions and rarefactions, producing a violent sound called 'thunder'.