Why Does Thunder Follow Lightening?
We often see lightening followed by thunder in the sky in rainy season.
Let us study why does thunder follow lightening?
In olden days, man used to believe that the gods were angry with him and was punishing him for some crime, when he saw lightening in the sky and heard thunder. In 1872 the occurrence of lightening was scientifically explained by Benjamin Franklin. In reality, when the sky becomes cloudy, the small particles of water present in the clouds get charged because of air friction. During this process some clouds get positively charged while the others get negatively charged. When the clouds having positive charge come close to negatively charged cloud then there develops a potential difference of millions of volts between them. Due to this high voltage, suddenly there is an electric discharge through. The air between the positively and negatively charged clouds and then a flash of light is seen. This is known as ‘lightening’. A large amount of heat is produced by the electric discharge through the air.
Because of this heat the suddenly the atmospheric air gets expand and the numerous molecules of air collide with one another and producing sound. This sound is called ‘thunder’. Actually the lightening and thunder are produced simultaneously but we first see the flash of light. This is due to the velocity of light, as it is very high i.e. 300000 kms per second, whereas the velocity of sound is 332 meters per second. So because of high velocity, the light reaches instantly in our eyes, but the sound takes some time to reach in our ears. When a cloud having charge passes by a high building or a tall tree, then by induction, it produces the opposite charge on that building or tree. If the so produced charge is very high then the sudden electric discharge in the air hit such building or tree. Fix the pointed rods made of copper or other metal on the top of the building to protect them from lightening. These rods pass through the building and are buried deep in the earth. These rods are called ‘lightening conductors’. When a cloud with some charge passes by this building and produces the opposite charge on it, then the charge does not damage the building as it goes to the earth through the rod. In this way we protect the building from the lightening.
