Knowledge Place

Fax or Facsimile transmission is a system of sending information on paper by telephone lines. It transmits a copy of the information document to another person in another city or country. It can also transmit drawings in addition to printed text.  Before sending a document, the fax machine tests the telephone line it is going to use. If it detects a faulty line, it automatically switches to a slower speed. This reduces the risk of losing the content of the information during transmission. The document is scanned and the image is converted into electric signals. At the receiver’s end of the telephone, another fax machine receives the signals, decodes them, and prints out a copy of the original document. 

Fossils are the remains of prehistoric animals and plants. They could be thousands of millions of years old. A fossil or the rock in which it is found is slightly radioactive. By measuring this radioactivity, the age of fossils can be determined. Over a span of time, the radioactivity of material decreases to zero. It may take thousands of millions of years for the material to lose its radioactivity. Plants and animals contain small amounts of radioactive elements. This radioactivity begins to decrease as soon as they die. Measuring this radioactivity, thus gives their age. 

The elements have atoms of two or more different weights. Atoms that belong to the same element and yet have different weights are called isotopes. The isotopes of an element have the same number of protons in each of their nuclei, but a different number of neutrons. Hydrogen has three isotopes namely, protium, deuterium and tritium. Nearly all the elements, except a few like gold, manganese etc., have isotopes. The isotopes are generally stable, but some elements have unstable radioactive isotopes. Such isotopes are useful in industry and medicine. The radiation from isotope Cobalt 60 is used to take photographs through metals and to detect cracks and other faults. Radioactive isotope scanning is used by doctors to study the working of internal organs.

Crystals are solids found in nature that have a regular three-dimensional shape. They come in an almost endless variety of sizes and shapes. All crystals have an orderly shape due to the internal arrangement of the atoms, ions, or molecules making up the solid. Crystal formation can be watched easily at home. Add sugar to water and let it dissolve. Now heat the water solution and let the water evaporate. Gradually, all the water evaporates leaving the crystals of sugar behind. 

Salt is a compound found in seawater. It makes up four-fifths of the substances dissolved in the sea. It is also found in underground deposits that can be dug out of the ground. To get salt, seawater is let into shallow pools at the shore. The sun’s heat makes the water evaporate, leaving the salt behind. Salt obtained from either of the two sources is not pure. To make it fit for consumption, it is purified. The salt is dissolved in hot water forming the brine solution. Brine is then evaporated to leave pure crystals of salt behind. 

A thing that is smooth looks shiny. This is due to the reason that it reflects all the light towards us. A rough surface does not do this if it is dry, but if it is wet, the water makes it smooth because water gets into the tiny holes of the surface and gives it a shine look.  When the light rays strike a rough surface, they are reflected in different directions at different angles, so it does not appear shiny. While when the light rays strike a smooth surface, all the light rays are reflected back at the same angle giving it a brighter look. The surface of water is completely smooth and is, therefore, shiny. A wet surface, therefore, shines as well.

Holograms are three-dimensional photographs, which have depth, length, and breadth. When a hologram is lit by laser light, it produces a three-dimensional image of an object. One can get a different view of the object as one walks around. To make a hologram, the object is lit by light from a laser. This light reflects from the object and strikes a photographic plate placed nearby.  At the same time, the laser beam is split so that it also reflects from mirrors and strikes the plate directly.  Interference between the two beams produces a pattern on the plate that is not recognizable as a photograph. This pattern is called a hologram. 

A balloon is filled up with a gas, usually hydrogen, that is lighter than air. The hydrogen in the balloon does have some weight, but the density of hydrogen is lower than that of air. This means that a balloon weighs less when filled with hydrogen in comparison to a balloon filled with the same amount of air. Since the balloon is lighter than air, it rises up into the air. If the balloon is filled with the air, the air inside is neither heavier not lighter, but the rubber of balloon makes it heavier than air and it sinks.

Plastics are synthetic materials which are made from chemicals that come from coal and oil. When chemicals are heated, they combine together to make plastics. These chemicals have small molecules. When plastics form, the molecules join together in long chains to make large molecules known as polymers. Plastics are of two types thermo plastics and thermosetting plastics. When thermoplastics are heated, they become soft and can be shaped and moulded. Polyvinyl chloride are examples of thermoplastics. Thermosetting plastics, when formed, set hard and stay rigid. Silicones and epoxy resins are some thermo settings plastics.  

A vacuum flask keeps things hot for several hours because it stops heat from escaping as far as possible. It is designed to prevent heat loss. The silver walls of the container inside the flask reflect heat rays back into the container.  There is also a vacuum between the walls of the container to stop heat from flowing through the walls. The container is surrounded by an outer shell made up of insulating material that decreases the loss of heat. The flask, thus, loses very less heat and keeps hot for a long time. 

Most bridges rest on supports called piers. A well is built in the river to keep out water, and the piers are fixed in the bed of the river.  The bridge is then built on the piers. The suspension bridges are built by fixing cables across a river from high towers on each side. The road is hung from the main cables. Cantilever bridges are made in two sections, each supported on a pier near each end of the bridge. The sections meet in the middle of the bridge, giving a long span to it. 

Sonar is a system used to locate things underwater, to measure the depth of sea underneath a vessel and to locate a shoal of fish.  It was invented in 1915 by Professor Langevin in France to detect icebergs following the sinking of Titanic in 1012.  Sonar takes its name from sound navigation and ranging. It works like radar except that sonar uses sound signals instead of radio signals. Sonar works by transmitting short bursts of sound and picking up reflections or echoes bouncing back from the obstacles in their path. The distance of the obstacle is calculated from the time interval between the transmitted and reflected pulses. The frequency of sound used is so high that it is beyond the highest frequency that can be heard by the human ear. The sonar screens use sound waves to build up pictures. 

Soap is used for washing. It makes the grease dissolve in water, because it is usually the grease that holds dirt and dust stuck on to the clothes. Ordinary water does not remove dirt from things because the grease and water cannot mix.  Soap is made of long, thin molecules that attach themselves to water molecules at one end and to grease molecules at the other end. The soap molecules, thus, link the water and grease molecules, so that the grease dissolves and is washed away with the water. Shop is made by heating fat or vegetable oil with a strong alkali, such as sodium hydroxide (Caustic Soda)

The telephone was invented by Alexander Graham Bell in 1876. It transmits speech in the form of electric currents. The mouthpiece of a telephone contains a small carbon microphone. the sound waves produced by our voice make a metallic diaphragm vibrate which squeezes the carbon granules of the microphone. An electric current flows through the microphone and the granules very its strength as we speak. this varying current then flows along wires to the telephone exchange, which sends it on to the other telephone. There it enters a Small loudspeaker in the earpiece. The earpiece contains an electromagnet which causes a diaphragm to vibrate as the incoming current varies. This produces the sound of our voice. 

The bulb has a thin wire called a filament, made up of tungsten. tungsten has a very high melting point, so the filament does not burn even when it gets white-hot. the bulb also contains a gas called argon which does not combine with tungsten to burn out. when we switch on a bulb, electricity passes through the bulb. when it reaches the filament, it makes it hot so that it glows. actually, the filament resists the flow of electrons. the greater the resistance, the hotter it glows.

Vitamins and minerals are present in our body in very small amounts, but are very important for the health of the body. Their deficiency causes many types of disease. The body requires only one hundredth of a gram of vitamin B every day and its deficiency causes a disease known as beri-beri. This vitamin is found in bread and meat. Vitamin A is found in corrots and liver and without it we suffer from night blindness. Vitamin C is present in fresh fruits and vegetables. It’s absence from the body causes the disease scurvy. Minerals are equally essential for the body. Iron present in meat, eggs and bread is needed to make the blood pigment hemoglobin. Calcium from milk, cheese and bread and phosphorous are required for the growth of bones and teeth.

Sweating is an important process to cool down the body when we get too hot. Is is produced by seat glands on the surface of the skin. As the sweat evaporates, the body cools down. Our body maintains a normal temperature. When we perform some strenuous work or exercise, the body tends to have a high body temperature. The heat goes out in two ways. The tiny blood vessels in the skin increase in size and let blood fill them so that the heat travels out from the blood to the air. This gives us a flushed appearance. When the body becomes hotter, the sweat glands produce a mixture of water and waste chemicals known as sweat. To evaporate water uses a great amount of heat. So does the sweat. A evaporates; it takes the heat rapidly from our body.

To attract insects for pollination, some plants have adopted a unique strategy. Instead of having sweet smelling flowers, they have ones stinking with rotten smell. This attracts many pollinating flies. The lords and ladies plants emit rotten smell from its spike that sticks out of the top. Flies get attracted by this stinking smell and fall inside the sheath. They pollinate the female flowers with the pollen brought from other plants and arte then showered with pollen from this flower. The world’s largest flower Fafflesia also attracts insects by it’s stinking smell and dark red, brown petals.

Flowers have male and female organs, i.e., anther and stigma, and they perform the function of producing seeds. The transfer of pollen from an anther to a stigma is understood as pollination and is that the first stage within the reproduction of plants. The flowers, in many cases, are pollinated by insects and to draw in the insects, flowers have bright colours and sometimes produce sweet scent and nectar. The flowers have bright colour to attract the insects. While drinking the nectar of the flower, an insect picks up pollen on its body and when it visits another flower, it brushes some of this pollen on to the stigma, thereby making cross pollination. Insect pollinated flowers are usually blue, yellow, pink or white. In some regions, birds, bars, rodents and marsupials help in pollinating flowers. These flowers too, are very brightly coloured.

To survive in the cold during winters, the deciduous trees shed their leaves. They live leafless for many months, thereby conserving water and avoiding frost damage. As the temperature begins to fall at the onset of autumn, the soil gets too cold for most broad based leaves to take up enough water. To avoid further loss of water by transpiration, the trees begin to shed their leaves. The trees begin to withdraw the chlorophyll before the leaves is shed, imparting various brilliant color to them depending upon the pigment left behind. Some evergreen trees like pine never lose their leaves even though they inhabit colder regions. They have thin, needle like leaves that have loss transpiration rate and, hence very low water loss.