A rule of thumb for estimating the distance in kilometers between an observer and a lightning stroke is to divide the number of seconds in the interval between the flash and the sound by 3. Is this rule correct? Defend your answer.
Solution 30E Step 1 of 2: The speed of sound in air is about 333 m/s, whereas the speed of light is 3 million m/s ( 3 × 10 m/s). Which means , for most of the practical cases, the speed of light is instantaneous. Therefore, we see the flash at the same instant when it happens, whereas the sound travels at 333m/s , we hear the sound later. To travel 1 kilometer, sound takes 3 seconds, 1000 m 333 m/s 3 seconds Therefore, the approximate rule (3 seconds per kilometer) is correct.