b. A seeing a lightning starts counting seconds he hears thunder. He then claims to have found an approximate but simple rule that the count of second is divided by an integer, the result directly gives, in km, the distance of the lightning source. What i (2024)

FAQs

When a man seeing a lightning starts counting seconds? ›

A man seeinga lightningstarts countingseconds, until he hears thunder. He then claims to have found an approximate but simple rule that if the count of second is divided by an integer, the result directly gives, in km, the distance of the lightning sotirce.

The speed of sound does vary based on temperature and humidity, but a good rule of thumb is that sound travels a mile every five seconds. Count the seconds between lightning and thunder, divide by five, and that's how many miles away the storm is.

If you count the number of seconds between the flash of lightning and the sound of thunder, and then divide by 5, you'll get the distance in miles to the lightning: 5 seconds = 1 mile, 15 seconds = 3 miles, 0 seconds = very close. Keep in mind that you should be in a safe place while counting.

The time for the thunder to reach the person is (1.6 × 10³ m)/(343 m/s) = 5 s. Thus, the time interval between seeing the flash and hearing the thunder is about 5 seconds for every mile of travel.

In nature, a lightning flash and the associated thunder occur at almost the same time in a thunderstorm. A person on the ground sees the lightning flash before hearing the thunder because light at a speed of around 300,000,000 meters per second travels much faster than sound which moves at 340 meters per second.

We are given that the thunder is heard after 4 seconds, $t=4s$ and we know the speed of sound is $v=340m/s$. So, we can make use of the formula: $d=vt$, to find out the distance at which the lightning occurs. Hence, the distance the lightning occurred is 1360 m. This is close to 1380 m mentioned in the options.

→ The distance of the nearest point of lightning = speed × time =346ms−1×2s=692m.

When you see the flash of a lightning bolt, you can start counting seconds and then divide to see how far away the lightning struck. If it takes 10 seconds for the thunder to roll in, the lightning struck about 2 miles or 3 kilometers away.

Assume that, in our case, it's 15 seconds. Calculate the storm distance. If you want to know approximately how far away the lightning is in miles, divide the number of seconds by 5; for kilometers, divide the seconds by 3. It will give us 3 miles or 5 kilometers.

Why does thunder take about a second to hear when lightning strikes 20 meters away? Light travels much faster than sound. This explains why, for example, when you see lightning strike a kilometer away the sound takes about three seconds to be heard.

How fast is lightning in seconds? ›

Lightning moves at the speed of light, darting across the sky at about 186,000 miles per second. Compare that to thunder, which moves at the speed of sound. At sea level, that's about 1 mile every 5 seconds.

If we are watching the sky, we see the lightning before we hear the thunder. That is because light travels much faster than sound waves. We can estimate the distance of the lightning by counting how many seconds it takes until we hear the thunder. It takes approximately 5 seconds for the sound to travel 1 mile.

Thunder starts as a shockwave from the explosively expanding lightning channel when a large current causes rapid heating. However, it is possible that you might see lightning and not hear the thunder because it was too far away. Sometimes this is called “heat lightning” because it occurs most often in the summer.

At the time of Lightning, flash, and thunder are emitted at the same time. As the light travels faster than the sound, the flash can be seen almost at the time of lightning. But the sound of thunder is heard after a few seconds of lightning.

It takes approximately 5 seconds for the sound of thunder to travel a mile. So, when you count the number of seconds between seeing a crack of lightning and hearing the thunder, divide that number by 5 and that is how many miles away the lightning was when it struck.

THE ANSWER: No, counting seconds between lightning and thunder to calculate the miles for every second is inaccurate. Instead, you must divide by five to know how close it is.

However, it is possible that you might see lightning and not hear the thunder because it was too far away. Sometimes this is called “heat lightning” because it occurs most often in the summer.

“The '30-30 Rule' directed people to be in a safe place when there is 30 seconds or less between lightning and its thunder, and to wait 30 minutes or more after hearing the last thunder before leaving the safe place.