A Sound Of Thunder Dubbed Hindi Movie Free Download Torrent
Nichelle Gruger
From the clouds to a nearby tree or roof, a lightning bolt takes only a few thousandths of a second to split through the air. The loud thunder that follows the lightning bolt is commonly said to come from the bolt itself. However, the grumbles and growls we hear in thunderstorms actually come from the rapid expansion of the air surrounding the lightning bolt.
Because electricity follows the shortest route, most lightning bolts are close to vertical. The shock waves nearer to the ground reach your ear first, followed by the crashing of the shock waves from higher up. Vertical lightning is often heard in one long rumble. However, if a lightning bolt is forked, the sounds change. The shock waves from the different forks of lightning bounce off each other, the low hanging clouds, and nearby hills to create a series of lower, continuous grumbles of thunder.
Thunder is the sound caused by a nearby flash of lightning and can be heard for a distance of only about 10 miles from the lightning strike. The sound of thunder should serve as a warning to anyone outside that they are within striking distance of the storm and need to get to a safe place immediately!
Thunder is created when lightning passes through the air. The lightning discharge heats the air rapidly and causes it to expand. The temperature of the air in the lightning channel may reach as high as 50,000 degrees Fahrenheit, 5 times hotter than the surface of the sun. Immediately after the flash, the air cools and contracts quickly. This rapid expansion and contraction creates the sound wave that we hear as thunder.
Although a lightning discharge usually strikes just one spot on the ground, it travels many miles through the air. When you listen to thunder, you'll first hear the thunder created by that portion of the lightning channel that is nearest you. As you continue to listen, you'll hear the sound created from the portions of the channel farther and farther away. Typically, a sharp crack or click will indicate that the lightning channel passed nearby. If the thunder sounds more like a rumble, the lightning was at least several miles away. The loud boom that you sometimes hear is created by the main lightning channel as it reaches the ground.
Since you see lightning immediately and it takes the sound of thunder about 5 seconds to travel a mile, you can calculate the distance between you and the lightning. 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. Remember, if you can hear thunder, chances are that you're within striking distance of the storm. You don't want to get struck by the next flash of lightning.
Where there is lightning there will be thunder, and where there is thunder there will be lightning. The reason: thunder is the sound of the shockwave that lightning produces as it heats up the air to 30,000C in less than one second. This is five times the temperature on the surface of the sun! The air surrounding the lightning channel or pathway expands explosively and creates a shockwave which produces the sound waves of thunder.
Have you ever wondered why the rumble of thunder can sound differently from one lightning strike to another? Depending on atmospheric conditions, you can hear thunder from as far away as 20 km, or as close as 8 km. How thunder sounds depends on a number of factors: the distance between you and the lightning strike, the temperature of the air, the amount of cloud and water in the air, as well as where the lightning channel is in relation to where you are situated.
Light travels at 300,000 km/second, whereas sound travels at 0.3 km/sec. This is why you can see the flash of lightning sooner than you hear the rumble of thunder that the initial lightning strike produces. As the distance to the lightning strike increases, the pitch of the thunder lowers. This is because the higher frequencies are selectively absorbed. This is just like when there is music playing in another room, you can hear the bass notes but not the high notes.
Sound waves are affected by the air temperature: they move faster in hot air and slower in cold air. They also bend or refract toward areas of lower temperatures similar to how light bends when it moves from air through water. Since the atmosphere usually cools with height, sound waves or thunder tend to deflect upwards. Typically this means if you are on the ground, more than 20 km away from a lightning strike, you will not be able to hear it. See figure A.
There are also differences over water because of the higher humidity near the surface of the water. The bending of the sound waves is enhanced because of the higher humidity so more of the sound waves are blocked. This means the storms have to be closer to you for you to hear the thunder. Lightning could be as close as 8 km away before you actually hear it which would place you within striking distance of being hit by lightning.
The sound of thunder will also sound different depending on whether the channel of lightning is associated with cloud to cloud lightning overhead (parallel) or cloud to ground lightning to the side of you (perpendicular).
But what happens if there are a number of strikes at once? In this case, sound waves from each part of the strike will reach you at different times and so you may hear a combination of claps and rumbles.
As noted above, light travels at 300,000 km/second, whereas sound travels at 0.3 km/second. Keeping this in mind, once you have transported yourself to a safe location, either in a house or car, you can calculate the distance of the lightning strike. After the flash of lightning, begin counting off the seconds until the thunder is heard. Divide the seconds by three to arrive at the distance in kilometres.
Listening to what thunder sounds like from various distances can be a fun experiment! Just remember that no matter how far away you see lightning, if you hear thunder, you are within striking distance of being hit. Find shelter immediately, either in a house or a car, and stay there for 30 minutes after the last rumble of thunder is heard before resuming your activities. But remember that every thunderstorm has a very first lightning strike that will come without any warning and could occur in your immediate vicinity. So even before thunder roars, you need to keep an eye on the sky.
However, when the air temperature increases with height, called an inversion, sound waves are refracted (bent back toward the Earth) due to their faster motion in the warmer air. Normally, only the direct sound of thunder is heard. But refraction can add some additional sound, effectively amplifying the thunder and making it sound louder.
If the lightning in these "elevated thunderstorms" remains above the inversion, then most of the thunder sound also remains above the inversion. However, many of the sound waves from cloud-to-ground strikes remain below the inversion, giving thunder a much louder impact.
During a recent thunderstorm in an urban area, I saw lightning strike within about half a mile, estimated as such because I heard the thunder about 2 seconds after I saw the strike. What surprised me was that I heard an electrical-sounding bzzzzt that was simultaneous with the strike, and lasted for the fraction of a second that the bolt was visible. This sound could not have come from the lightning bolt itself, as I heard it well before the thunder.
There are power lines not far outside my window. Did the lightning strike send a surge through the grid from half a mile away that was heard at my house? This is about the only explanation I can think of for the timing of the sound. If it did, what actually causes that bzzzt noise?
What you heard was probably due to nearby static discharges that were triggered by the lightning strike. The E&M field during a thunderstorm is very complex and sudden changes travel at $c$ (the speed of light in a vacuum) so objects can produce static discharges before the sound of thunder arrives. I was standing on a wooden deck with a metal handrail once when a nearby lightning strike occurred and heard a buzz coming from the handrail prior to the thunder.
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