Category Physics

WHY DOES A PENCIL APPEAR BENT IN WATER?

When a pencil is put in a glass of water, it would appear bent because of refraction of light. Refraction is the bending of light as it passes from one transparent substance into another. Light waves can’t travel as quickly in water as it does in the air. Hence they bend around the pencil, causing the pencil to look bent in the water. Further, the light refraction gives the pencil a slight magnifying effect, which makes the angle appear bigger, causing the pencil to look bent. It all has to do with the fact that light travels more slowly in water than it does in air, and that causes the light to bend when it goes from water to air, or vice versa. How the light bends depends on the shape of the water surface and the angle at which the light hits it.

It is the same “magnifying lens” phenomenon that makes things look fatter when viewed through a glass of water. In that case, the fattening effect is doubled, because the beam of light widens both when it enters the water through a curved surface and when it leaves through the other side.

Credit : Orlando sentinel

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WHY IS THE STRATOSPHERE VITAL?

The stratosphere has a layer of ozone gas, which acts like a thick umbrella covering the layers beneath. By absorbing most of the harmful UV radiation from the Sun, the ozone layer prevents it from reaching the surface of the Earth, thus enabling the survival of life on the planet.

Stratosphere could be aptly called the ‘protection blanket’ of Earth. It extends up to 600 kms from the surface of the earth and it is the second layer of the Earth’s atmosphere, right above troposphere.

Stratosphere houses in it the most important layer called Ozone (O3), which acts as an absorber of the harmful UV radiations of the Sun (of about 90%) and thereby protecting us from diseases like Cancer, skin burn etc.

Its non-turbulance and stable, non-convection character makes it possible for the jets to cruise easily, hence they are flown here.

When Volcanic eruptions occur, the ejected material reaches as high as Stratosphere and it stays there for long period, as it doesn’t allow the circulation, there by leading to stratifying the volcanic particles and cooling down of the Earth surface.

However, such an important layer is being perforated by us through the extensive use of the chloro-fluro-carbons which happen to destroy the ozone molecules.

There is also an idea which the scientists are considering that could result in the slowing down of the Earth’s heating, i.e., by adding the man-made materials to stratosphere. Though the feasibility of this idea is yet to be verified. Thus, is the importance of the Stratosphere layer.

Credit: medium.com

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IS THE ATMOSPHERE BUILT UP IN LAYERS?

Yes, the atmosphere has five layers. The lowest layer, closest to the surface of the Earth, is the troposphere. This is where weather is made, and most of the atmosphere’s gases are concentrated in it. Above it is the Stratosphere. No winds blow in this layer, nor are there any clouds. Beyond it lies the cold mesosphere, with very few gases. It is followed by the thermosphere, the thickest and hottest layer of the atmosphere, and lastly, the exosphere, on the edge of outer space.

Earth’s atmosphere is all around us. Most people take it for granted. Among other things, it shields us from radiation and prevents our precious water from evaporating into space. It keeps the planet warm and provides us with oxygen to breathe. In fact, the atmosphere makes Earth the livable, lovable home sweet home that it is.

The atmosphere extends from Earth’s surface to more than 10,000 kilometers (6,200 miles) above the planet. Those 10,000 kilometers are divided into five distinct layers. From the bottom layer to the top, the air in each has the same composition. But the higher up you go, the further apart those air molecules are.

Troposphere: Earth’s surface to between 8 and 14 kilometers (5 and 9 miles)

This lowest layer of the atmosphere starts at the ground and extends 14 kilometers (9 miles) up at the equator. That’s where it’s thickest. It’s thinnest above the poles, just 8 kilometers (5 miles) or so. The troposphere holds nearly all of Earth’s water vapor. It’s where most clouds ride the winds and where weather occurs. Water vapor and air constantly circulate in turbulent convection currents. Not surprisingly, the troposphere also is by far the densest layer. It contains as much as 80 percent of the mass of the whole atmosphere. The further up you go in this layer, the colder it gets.

Stratosphere: 14 to 64 km (9 to about 31 miles)

Unlike the troposphere, temperatures in this layer increase with elevation. The stratosphere is very dry, so clouds rarely form here. It also contains most of the atmosphere’s ozone, triplet molecules made from three oxygen atoms. At this elevation, ozone protects life on Earth from the sun’s harmful ultraviolet radiation. It’s a very stable layer, with little circulation. For that reason, commercial airlines tend to fly in the lower stratosphere to keep flights smooth. This lack of vertical movement also explains why stuff that gets into in the stratosphere tends to stay there for a long time. That “stuff” might include aerosol particles shot skyward by volcanic eruptions, and even smoke from wildfires. This layer also has accumulated pollutants, such as chlorofluorocarbons. Better known as CFCs, these chemicals can destroy the protective ozone layer, thinning it greatly. By the top of the stratosphere, called the stratopause, air is only a thousandth as dense as at Earth’s surface.

Mesosphere: 64 to 85 km (31 to 53 miles)

Scientists don’t know quite as much about this layer. It’s just harder to study. Airplanes and research balloons don’t operate this high and satellites orbit higher up. We do know that the mesosphere is where most meteors harmlessly burn up as they hurtle towards Earth.

The mesopause is also known as the Karman line. It’s named for the Hungarian-born physicist Theodore von Kármán. He was looking to determine the lower edge of what might constitute outer space. He set it at about 80 kilometers (50 miles) up.

The ionosphere is a zone of charged particles that extends from the upper stratosphere or lower mesosphere all the way to the exosphere. The ionosphere is able to reflect radio waves; this allows radio communications.

Thermosphere: 85 to 600 km (53 to 372 miles)

The next layer up is the thermosphere. It soaks up x-rays and ultraviolet energy from the sun, protecting those of us on the ground from these harmful rays. The ups and downs of that solar energy also make the thermosphere vary wildly in temperature. It can go from really cold to as hot as about 1,980 ºC (3,600 ºF) near the top. The sun’s varying energy output also causes the thickness of this layer to expand as it heats and to contract as it cools. With all the charged particles, the thermosphere is also home to those beautiful celestial light shows known as auroras. This layer’s top boundary is called the thermopause.

Exosphere: 600 to 10,000 km (372 to 6,200 miles)

The uppermost layer of Earth’s atmosphere is called the exosphere. Its lower boundary is known as the exobase. The exosphere has no firmly defined top. Instead, it just fades further out into space. Air molecules in this part of our atmosphere are so far apart that they rarely even collide with each other. Earth’s gravity still has a little pull here, but just enough to keep most of the sparse air molecules from drifting away. Still, some of those air molecules — tiny bits of our atmosphere — do float away, lost to Earth forever.

Credit: Science news for students

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WHAT IS THE IONOSPHERE?

It is another layer, overlapping the mesosphere, thermosphere and exosphere, where radio waves are reflected.

A dense layer of molecules and electrically charged particles, called the ionosphere, hangs in the Earth’s upper atmosphere starting at about 35 miles (60 kilometers) above the planet’s surface and stretching out beyond 620 miles (1,000 km). Solar radiation coming from above buffets particles suspended in the atmospheric layer. Radio signals from below bounce off the ionosphere back to instruments on the ground. Where the ionosphere overlaps with magnetic fields, the sky erupts in brilliant light displays that are incredible to behold.

Several distinct layers make up Earth’s atmosphere, including the mesosphere, which starts 31 miles (50 km) up, and the thermosphere, which starts at 53 miles (85 km) up. The ionosphere consists of three sections within the mesosphere and thermosphere, labeled the D, E and F layers, according to the UCAR Center for Science Education.

Extreme ultraviolet radiation and X-rays from the sun bombard these upper regions of the atmosphere, striking the atoms and molecules held within those layers. The powerful radiation dislodges negatively charged electrons from the particles, altering those particles’ electrical charge. The resulting cloud of free electrons and charged particles, called ions, led to the name “ionosphere.” The ionized gas, or plasma, mixes with the denser, neutral atmosphere.

Credit: Live Science

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Freakish wonders of the universe

The universe is full of deep mysteries and even the fraction of what we know is too fascinating for words. This month let’s take a look at some of the amazing yet scary inhabitants out there.

I’m coming to visit you

Black holes form when huge stars collapse and grow, taking up other objects around them. Think of them as giant invisible blenders that can tear apart planets even thousands of miles away. There aren’t black holes anywhere close to our solar system, but did you know that they can actually travel through space? And scarier still, rapidly-moving black holes cannot be detected! Scientists have assured us that space is a big place and black holes are quite rare – so sit back and relax!

A big show off!

Ever heard of gamma ray bursts? Well, they are considered as the brightest electromagnetic events to occur in the universe, so much so, that they can be seen billions of miles away! Are you also wondering how powerful they are? Apparently they emit as much energy in a few seconds that our sun can in 10 billion years! We’re glad that, like black holes, they are rare and far, far away from us.

Lone travellers

We imagine planets going around a star, endlessly orbiting it as long as they live. It turns out that not all planets exist this way. Astronomers have discovered a few Jupiter-sized planets drifting alone, without a place to call home or a star as a boss. They are thought to have been ejected out of their star system due to some massive explosion event. As long as they are not on a trajectory towards Earth, it’s dreamy fun to think about these lonely nomadic travellers.

What a blast!

Earth is like a magnet but its magnetic field is quite weak; an MRI machine can produce a magnetic field thousand times stronger. Since we can put our head in through the MRI machine, we can obviously put up with that magnetic field. But imagine a magnetic field that is a trillion times stronger than that of Earth. That’s the kind of power that a magnetar possesses! Come within 1000 kilometres of a magnetar and the very molecules that make you up can dissolve! Here’s a fun fact to freak you out in 2004, a magnetar located halfway across the Milky Way (500 quadrillion kilometres away) quaked and its effect was felt on the Earth’s upper atmosphere!

Mission Impossible

What if you stepped too close to a black hole but not quite? That’s exactly what hypervelocity stars did! They bolted away from the black hole at superfast speed. Hypervelocity stars were originally binary stars, of which one was captured and gobbled up by the black hole at the centre of our galaxy while the other lucky star was sent rocketing off at a very high speed, obviously very, very glad to escape.

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HOW MANY HOURS ARE THERE IN A DAY?

Our system of telling time is based on the premise that every day is exactly 24 hours long — quite precisely, with no exceptions. This concept is fully ingrained into our culture, a core principle of our modern technological society. At the same time, we are taught in school that a day corresponds to one complete rotation of the Earth on its axis. Unfortunately, these two concepts don’t quite match up — and the mismatch is more than just a few milliseconds. In fact, the mismatch amounts to several minutes every day. Furthermore, because our traditional concept of a “day” is actually defined by the cycle of sunlight and darkness — and not by one rotation of the Earth — the length of a real day is not consistent, but varies somewhat during the year. We only pretend that all days are the same length — by averaging the length of all the days in the year, and then defining this average as a “standard day” of exactly 24 hours.

This is not a bad thing. In fact, it has been quite helpful to define our system of time in this manner. But once you understand why this system does not quite match up with the real world, then you can begin to make sense of several interesting phenomena. For example, you would think that the earliest sunset and the latest sunrise would both occur on the shortest day of the year, which is the first day of winter. But this is not the case at all.

If our definition of a day was truly based on one complete rotation of the Earth on its axis — a 360 degree spin — then a day would be 23 hours, 56 minutes, and 4 seconds. This is nearly 4 minutes shorter than our 24-hour standard day. However, our concept of a “day” has long been based on the natural cycle of sunlight — a period of daylight followed by a period without daylight. The mismatch of nearly 4 minutes is because the Earth must rotate more than 360 degrees between one dawn and the next. As you know, the Earth experiences two simultaneous motions — it not only spins on its axis, but it also travels in orbit around the sun. In a period of one day, the Earth travels about 1/365 of the way around the sun (because it takes about 365 days to go all the way around, which is how we define a year). This daily progress in the Earth’s orbit is almost exactly a degree (defined as 1/360 of a circle). Therefore the Earth has to spin an extra degree in order to line up with the sun again each day. The result is that one complete cycle of sunlight and darkness — one day — represents a rotation of about 361 degrees, not 360 degrees. Although a year consists of 365 and a quarter days, the Earth actually spins 366 and a quarter times during a year. From the standpoint of sunrises and sunsets, one complete spin is negated each year by the journey around the sun.

Credit: medium.com

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