Question

A common acoustic phenomenon is thunder, the rapid heating and supersonic expansion of air created by a lightning stroke. Because the speed of light reaches almost any point on Earth instantly while sound travels more slowly, the time lag between lightning and thunder can be used to estimate distance to the lightning. This delay time is ______ seconds per kilometer (5 sec/mi).

Answer 1

Answer:

Δt ≈ 2.9137 ≈ 3 seconds per kilometer

Explanation:

The speed of light is approximately 300000 km /s, while the speed fo the sound in the air is 0.3432 km/s.

The light takes  therefore  this time to travel one kilometer

$x = vt$              $t = \frac{x}{v}$

$t = \frac{1}{300000}$

$t = 3.33 x 10^{-6} s$

On the other hand the sound takes this time to travel one kilometer

$t = \frac{1}{0.3432}$

t = 2.9137 s

Then the delay time is 2.9137 - $3.33 x 10^{-6} s$

Δt ≈ 2.9137 ≈ 3 s