The word radar stands for radio detecting and ranging. It makes use of very short radio waves called microwaves. Radars work to find out how far away an Object is and in case of a moving object in what direction it is moving and at what speed.
COLOR TV PICTURE PRODUCED
The picture on a television screen is nothing but a pattern of glowing dots, or pixels. The pixels are made up of fluorescent chemicals called phosphors that are coated on the back on the screen. These glow on being hit by a beam of a single phosphorus and are lit up by a single electron beam that rapidly sweeps across the screen. In a color television how-ever, each pixel contains three phosphorus each producing a different colour- green, red and yellow. Three electron beams produced by three electron guns are used to light up the different phosphorus.
FIRE EXTINGUISHERS WORK
Fire extinguishing agents work basically in two ways – either by cooling the burning materials or by blanketing them with an inert coating that cuts off the supply of oxygen. One of the most common ones uses water which has a high heat capacity.
Foam type fire extinguishers use foaming agents that have a smothering and cooling effect on the wire. A dry chemical extinguisher sprays a very fine power of sodium bicarbonate or potassium bicarbonate or monoammonium phosphorus. These solids coat the fuel and smother the fire. A safe and effective extinguisher for all confined fires uses carbon dioxide (co2) which acts as an inert blanket.
LIE DETECTORS WORK
A lie detectors work on the principal that a person who tells a lie is nervous and under stress under these conditions his body undergoes some physiological changes.
These includes increases in the blood pressure, heart beat rate and perspiration on hands and soles. These changes are monitored and detected by a lie – detector.
STORAGE BATTERIES WORK
Storage batteries are devices which act as a store house of electrical energy. The electrical energy is stored in the form of a chemical charge which is reversible. The most common storage battery is the lead acid- accumulator which uses lead as electrode and sulphuric acid as an electrolyte. Initially both the cell electrodes of the battery made of lead are coated with a layer of lead dioxide. When the battery is charged for the first time, chemical charges take place. During discharging when the battery is in use, chemical changes take place again but in the reverse way. Each cell in a lead – acid battery produces two volts and a typical car battery with six cells gives 12 volts. Nickel – iron and nickel – cadmium batteries are other kind of storage batteries which are nickel, and iron or cadmium as electrodes and potassium hydroxide as electrolyte.
Aeroplanes fly by a combination of power from the engines and lift provided by the wings. These are shaped in such a way that air flowing along the upper surface takes a longer path than the air flowing along the lower surface. As a result when an aircraft moves forward, the air flowing above the wings moves faster than the air flowing below the wings, creating a low pressure above the wing according to Bernoulli’s law. This difference in pressure above and below the wings causes lift. As the speed of the aircraft on the runway increases, the lift also increases, eventually overcoming the download force of gravity. The aircraft also uses the thrust created by its engine to climb and after reaching certain height cruises along in a horizontal direction.
HELICOPTERS REMAIN STATIONARY IN MID AIR
Unlike an aeroplane, helicopters have moving wings in the shape of spinning rotor blades. Air currents passing over the upper and lower surface of the spinning blades crates low pressure above it and generate lift. The lift can be controlled by varying the pitch (angle) of the rotor blades, by increasing the pitch of the main rotor blades lift is increased and the craft climbs. Lowering the pitch of the blades lift is increased and the craft climbs. Lowering the pitch of the blades reduces lift and gravity causes the helicopter to descend. Similarly , if the pilot holds the rotor pitch in such a way the blades produce just enough lift to counteract gravity, the helicopter remains station ary in mid – air.
NIGHT VISION GLASSES WORK
Night vision glasses, used for seeing in the pitch dark night, use the little light available to form an image of sufficient brightness to be screen.
The image is first focused, as in a camera, on to a window which is coated with special chemicals containing sodium, potassium, cadmium and oxygen compounds which emit electrons when illuminated.
The electrons so emitted are then accelerated by a series of powerful electric fields and made to fall into another screen coated with a fluorescing chemical which glows recreating a much brighter image of the original scene. Some night vision glasses make use of infrared radiation emitted by all objects even in the dark. These radiations are amplified in a similar way to make night vision possible.
AIR POLLUTION DETECTORS WORK
Air pollution is coused by substance that is not normally part of the atmosphere’s composition. Important air pollutants are sulpher dioxide, nitrogen oxides and carbon mono oxide usually emitted in automobile exhausts and power smoke. Pollution detectors work by making use of the chemical or physical properties of the pollutants. For example, the detection of nitrogen oxides is based on the emission of light as a result of a chemical reaction. This phenomenon is called chemilumine-scences.
If nitrogen are present, light is emitted which can be detected by a photo detected. Sulphur dioxide is detected by introducing it into a flame and then analyzing the colour produced by an instrument called flame photometer. Carbon monoxide is detected by emission of infrared radiation of a particular frequency when excited by an arc or a spark. An infrared spectrometer is used to detect the presence of this gas in air.
An automatic teller machine (ATM) performs simple banking functions such as deposits withdrawal, cash dispensing, and transfers between accounts. An ATM is a terminal connected via telephone or dedicated telecommunication lines to larger computer system that identify the user’s account on the basis of data stored in a magnetic strip on the back of a plastic ATM card commonly known as the credit card. The user operates the system using an exclusive personal identification number (PIN), assigned to him or her.
ARTIFICIAL DIAMONDS MADE
Diamond is formed in nature from graphite beneath the earth crust by the action of extreme heat and pressure. Artificial diamonds are made by mimicking the natural process by applying intense heat and pressure on graphite in the presence of iron as catalyst. A pressure of up to 1, 00,000 kg per sq. Cm. is applied and an electric furnace is used for heating the compressed mixture up to 2500 C. On cooling, the molten mass contains, tiny artificial diamonds firmly surrounded by iron.
A pearl is a biological product produced naturally by certain oysters as a defense mechanism. They are formed when a foreign body such as a sand particle enters the body of the oyster. the oysters in order to get rid of the foreign body coasts it with a material called nacre which is basically the chemical calcium carbonate. Over a period of time these layers make the pearl grow in size until they are taken out. Pearls are cultured by inserting an artificial irritant into the oyster. The oysters are then carefully tended in special beds. Cultured pearls usually take three to six years to grow to a good size.
CRUDE OIL REFINED
Crude oil that comes out of an oil well is a thick, dark liquid containing a mixture of many organic compounds. It cannot be put to use without refining. The different constituents of crude oil boil at different temperature. Refining processes may be classified as fractional distillation separates crude oil into some of its fractions depending on their boiling points. Some components are separated by solvent extraction in which an organic solvent is used to extract the substances especially solids which are then recovered by crystallization or evaporation of the solvent. Cracking is also a process used in refiners to produce useful petrochemicals. Here heat and catalyst are used to break down some of the heavier hydrocarbons to lighter, more useful fractions.
COOKING OIL REFINED
Vegetable oils are mixtures of chemicals called glycerides or esters of glycerides and long chain fatty acids. Oil is obtained by crushing oil bearing seeds such as ground nut, sunflower seeds or rapeseed, and then pressing the oil through expellers.
These mechanically extracted oils contain impurities like gums and free fatty acids (FFA), which have to be removed to make the oils suitable cooking media. Refining of oils is done by first treating it with alkali which forms soap with the FFAs. The soaps settle out carrying with them some colouring matter. The colour and odour are removed by treating the oil with some absorbing materials like fuller’s earth. Refining can also be done by extracting the pure oil with a suitable organic solvent like hexane and then removing the solvent by distillation.
Photocopying makes use of materials which can be electrostatically charged and which loses the charge when exposed to light. In a photocopying machine a drum made up of selenium is first charged electrically in the dark. An image of the illuminated document to be copied is then projected on to the charged drum.
The illuminated areas in the image falling on the drum destroy the electric charge while the dark areas retain the charge. The drum is then dusted with a fine black resinous powder called toner image of the original document. The image is transferred to paper which is given the opposite charge. The toner image is finally fixed on the paper by applying heat which melts the toner and sets it into the fibers producing a permanent dry copy of the original document. The entire process is automated.
COLOR PAINTING DONE
A printed colour picture is made up of tiny dots of three primary colours-cyan, magenta, yellow, and black. For printing, there fore, the colour original is first separated by scanning into negatives for cyan, yellow, magenta and black. During scanning, a screen of dots is also used so that the images on the four negatives are in the form of fine dots which is necessary for printing.
The most popular colour printings process used these days is offsets printings. Offset printings employs specially treated aluminum plates on which the printings ink sticks only to selected areas. When the plate, made sensitive to light by chemical coating, is exposed to light through the film negative and washed, coated areas that repel water but accept oil based ink remain. The plate is mounted on a cylinder in printing machine and wetted so that only the printed areas are linked. The impression from the printing plate is first transferred to a cylinder covered with a rubber blanket which finally transfers the impression onto paper.
WE FALL ASLEEP
In humans the sleep wakefulness cycle is controlled by the hypothalamus located in the lower portion of the brain.
MEHANDI COLOUR SKIN
Mehandi or henna leaves contain a colouring matter called Lawsone. This is a dye which can bind with the protein in hair and nails. This protein is called keratin. The skin of the palms and soles also contain keratin.
Outside the body, blood coagulates in five to ten minutes. Coagulation involves alteration in one of the plasma protein called fibrinogen into an insoluble protein called fibrin with the help of calcium icons. Coagulation can, therefore, be prevented by removing the calcium icons from blood. For preservation of blood meant for transfusion, sodium citrate is added which removes calcium form blood by forming a soluble complex with it.
BODY TEMPERATURE MAINTAINED
The body has an in built temperature regulating mechanism in the shape of the hypothalamus in the brain. The heat of the blood passing through it and the messages sent from the temperature sensitive nerve endings on the skin feed information to the hypothalamus. Once region of the hypothalamus so sensitive to temperature above normal while another region is sensitive to a fall in body heat.
When the body gains too much heat it loses the extra heat by sweating. When the environment is cold, the body generates extra heat by stepping up metabolism and muscle activity such as shivering. These changes are brought by path ways controlled by the nerves that are concerned with reflex control of bodily functions.
AIDS is caused by a virus called human immunodeficiency virus or HIV. The presence of this virus is detected by screening the blood of a person for special kinds of proteins called antibodies which are produced in the body in response to viral infection A characteristic feature of antibody molecules is that they are highly specific. They bind only to certain regions of the antigen. This is similar to a key fitting only a specific lock. AIDS detection tests are actually based on detecting the binding of the antibodies present in the blood with an artificially synthesized antigen attached to a solid surface.
ALCOHOLIC BEVERAGES INTOXICATE
Alcoholic beverages contain ethyl alcohol which on reaching the brain and slows down the activity of the central nervous system especially those parts of the brain that control a person’s behavior.
BATS FLY IN THE SKY
Bats navigate by making use of sounds that they emit. The way these sounds bounce off from nearby objects and obstacles and return to the bat’s ears enables it to gauge distance and avoid obstacles. Being in the range of 100,000 hertz, these sounds are inaudible to human ears which can hear only unto 20,000 hertz.
Bats can discriminate between faint echoes of their own sound in the presence of other sounds. Interestingly. Large bats such as the flying fox do not use sound for navigating but rely on vision instead. They fly and feed by day and become disoriented if forced to fly in the dark.
CAMELS SURVIVE IN DESERTS
Camels can survive for days in desert with little food and no water due to their unique physiology. Contrary to the common belief, a camel does not store water serves as a reverse for energy and a source of water when in need. When the fat is utilized by the camels body, hydrogen is released which combines with oxygen to form water.
A firefly emits yellow-green light from special organs located in the lower portion of its abdomen. These organs contain in enzyme called luciferase which acts as a catalyst. When luciferin comes in contact with oxygen from air in presence of lucifrease, it gets oxidized emitting flashes of light. The light produced is, cool.
LIZARDS WALK ON WALLS
The feet of lizards are adapted for walking on rough as well as smoth surface. The lizards have slits on their toes and these functions like suction disks helping them to cling to smooth areas such as a glass pane. The claws present on toes help the lizard to hold on to and walk on a rough surface. in this way a lizard can even walk upside down across a plastered ceiling or on a glass roof without trouble.
ANIMALS SEE AT NIGHT
Members of the cat family, like the tiger and cat or other nocturnal animals can see in near darkness because of the presence of large number of cells called rod cells in the retina. These cells are sensitive to dim light and help the animal to see in near darkness. Other nocturnal animals like owl and Loris have very large pupils which allow more light to enter the eyes. In addition, the retina of these animals has a layer called ‘tapetum lucidum’. This reflects inwards the light falling on retina and thus help in gathering all the light available in dark surrounding.
Unripe fruits are typically hard, green, and have a sour on astringent taste due to the presence of organic acids such as malic, citric, and tartaric. They have high amounts of large molecule carbohydrates called polysaccharides and low amount of protein. Ethylene gas which triggers the ripening process emanates from fruits and causes rapid and dramatic changes. The green color of the fruits disappears and red, or yellow coloured pigments such as anthocyanins and carotenoids appear giving the fruits distinct colour.
The polysaccharides are broken down to smaller sugars which give the fruits the sweet taste. The fruits also begin to soften. Volatile substances are produced during ripening which gives many fruits their distinct aroma.
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