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Thunder

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-343

2025-11-30

670

 In the case of a lightning flash the air is the dielectric which is broken through, and since the velocity of the discharge is very great, it is probable that a compression wave is set up in the air like that which is set up by a flying cannon ball and that this wave striking the ear produces the sound of the thunder. Other causes may help to produce it, such as the restoring to a condition of rest of the air that has been broken through by the flash, or the formation of steam from the moisture in the air, caused by the heat of the discharge. To a person who is near the flash the sound is that of a crash, but to one at some distance the direct report is mingled with its echo from the clouds and the earth, producing the deep, rolling sound that we call thunder.