Using the flash-to-bang method, if the time between the flash and the bang is 11 seconds, what is the estimated distance?

• A. 1100 m
• B. 550 m
• C. 3850 m
• D. 770 m

Answer: (C)

Sound travels through air at about 343 meters per second. The flash-to-bang method uses the time delay between the lightning flash and the resulting thunder to estimate distance by multiplying that time by the speed of sound. With a delay of 11 seconds, the distance is roughly 11 × 343 ≈ 3,773 meters, about 3.8 kilometers. Among the given options, the distance closest to that is around 3,850 meters, so the estimate is about 3,850 meters. Remember, wind, temperature, and humidity can slightly change the speed of sound, so this is an approximate distance.