The flash of lightning, produced at a distance of 10 km above the ground level is seen much before hearing the thunder bolt. Find the time gap between the two events observed by a person on the ground if the time taken by the lightning to reach the surface of earth is negligible.
(velocity is sound `= 330 ms^(-1)` and velocity of light `= 3 xx 10^(8) ms^(-1)`.)

Explanation

Distance of clouds above the ground, (d) = 10 km `= 10 xx 10^3 m = 10, 000 m.`
Velocity of sound, (V) = 330 m `s^(-1)`.
Time taken to hear thunder,`(t_2) = (10^4 m )/( 330 m s^(-1))`
`=( 10^3)/(33 ) = (1000 )/(33) s= 30.30 s- (2)`
` therefore` time gap `( Delta t) = t_2 - t_1 = 30.30 – 0 = 30.30 s`