Question

A rule of thumb for estimating the distance in kilometers between an observer and a lightning strike is to divide the number of seconds in the interval between the flash and the sound by 3. Is this rule correct? Explain the reasons for its correctness or incorrectness

Answer 1

Velocity of sound at 20 ° C = 343 m/s

Let distance = d

Therefore, using velocity × time = distance.

343 × t1= d

T1 = d/343. ..(1)

Speed of light = 3× 10^ 8 m/s

Therefore, time (t2) = d/(3×10^8) ....(2)

Therefore, t1 - t2= d{ 1/343 - 1/(3× 10^8)}

∆t = d × 0.002915 (if distance is in m )

∆t = 2.915 d ( if distance is in km)

Therefore, we need to divide the difference of time interval by 2.915 and not by 3.

Thus , the rule is incorrect.

Please ask your doubts or queries in the comment section below.

Please kindly upvote if you are satisfied with the solution.

Thank you.