Question 42
MediumOriginal questionDuring a storm, Irfan sees a flash of lightning and hears the thunder 3 s later. Taking the speed of sound as 340 m/s, about how far away was the lightning?
Show the answer and explanation
CorrectNot quiteAnswer D
Correct answer: D
Explanation
Light arrives almost instantly, so the 3 s is the time the sound took.
Distance = 340 × 3 = 1,020 m, about 1 km.
Worth noting
510 m halves the distance as if it were an echo; thunder travels only one way. 340 m forgets to multiply by the time, and 113 m divides by it.
- Concept
- Speed of light and sound compared
- Typical timeTypical
- 60 s
- Your timeYours
- —
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