PGLAW 2016 Panjab University Entrance Exam With Answers

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47.

We See The Flash Of Lightning Before Hearing The Thunder Because :

A: Light Travels Faster Than Sound
B: Sound Travels Faster Than Light
C: Lighting Occurs Before Thunder
D: Thunder Occurs Before Lightning

The answer is: A

Explanation

The correct answer is A: Light Travels Faster Than Sound.

When lightning strikes, it produces a flash of light which travels at the speed of light, which is about 299,792,458 meters per second (or roughly 186,282 miles per second). Sound, on the other hand, travels through the air at a much slower speed, which is around 343 meters per second (or roughly 1,125 feet per second) at room temperature.

So when you see a flash of lightning, the light reaches your eyes almost instantly, while the sound of the thunder takes a longer time to reach your ears. This is why we see the flash of lightning before hearing the thunder.

In fact, you can use this time delay to estimate how far away a thunderstorm is from you. Since sound travels at a known speed, you can count the number of seconds between seeing the lightning and hearing the thunder, and then divide by 5 to get an estimate of how many miles away the storm is.