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Q60 (CAPF/2026) Science & Technology › Basic Science (Physics, Chemistry, Biology)

The brightness of a lightning event was seen at 19:06:17 hr, whereas the sound of the thunder in the same process was heard at 19:06:23 hr. If the speed of the sound is 320 metres per second, then which of the following is the distance in metres between the clouds that produced the lightning and the thunder, and the observer?

Result
Your answer: —  ·  Correct: C

Explanation

To calculate the distance, we first determine the time interval between seeing the lightning and hearing the thunder. The lightning was seen at 19:06:17 hr and the thunder was heard at 19:06:23 hr, which gives a time delay of 6 seconds (23 − 17 = 6).

Since the speed of light is extremely high (approximately 3 × 108 m/s), the time taken for the light to reach the observer is negligible. Therefore, the delay is essentially the time taken by the sound to travel from the clouds to the observer. Using the basic physics formula:

Distance = Speed × Time

Given the speed of sound is 320 m/s and the time is 6 seconds:
Distance = 320 m/s × 6 s = 1920 metres.

Thus, the distance between the observer and the source of the lightning/thunder is 1920 metres.

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