What is Compact disc?

Compact disc is a system of recording or storing of digital audio or video information using laser technology on a metal disc. The data is stored on a small aluminium disc in the form of microscopic pits etched by a laser beam. The stored information is read by using a laser beam which scans the rotating disc much like the replaying of phonograph records. The pits read as 0 and the smooth surface as 1, creating the sound digitally. As the laser beam does not wear out the surface, music replayed from an audio compact disc is without any distortion or noise and such music compact discs have virtually replaced phonograph records or turntables. The compact disc also allows recording and storage of text, pictures as well as sound simultaneously on a single disc and it has enormous capacity to store data. For example, the entire text and pictures contained in the 30-volume Encyclopedia Britannica can be stored on a single compact disc. Because of their versatility, adaptability and large storage capacity, compact discs are likely to be the choice medium for home entertainment and computer systems of the future.


What is Computer mouse?

Computer mouse is a device for manipulating figures on a computer screen without using a keyboard. It is an input mechanism that bears some resemblance to the animal. Computer operations often involve creating, selecting, or manipulating items on a screen. A computer mouse can perform these tasks by pointing or taking the cursor to the desired place, on the screen.

It is a hand operated pointing device that senses movements as it is dragged across a flat surface and conveys this information to the computer. In this way images, and text can be moved around on the screen, or a particular operation selected from a menu. A mouse usually has one or three buttons that are clicked when the user wants to register the cursors current position.

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What is Cryogenic engine?

A cryogenic engine is a liquid propellant rocket motor which uses liquid oxygen and liquid hydrogen as propellants. Weight for weight it produces a much higher thrust than rockets using other propellants. It is an essential part of any rocket used to launch geostationary satellites such as INSAT-2B. Since the propellants have to be stored at extremely low temperatures of around minus 200 degrees Celsius, the technology used here is quite complex. Indian scientists have already developed a prototype of a small cryogenic engine. India has successfully carried out the “full test firing” of a domestically developed cryogenic engine. This has propelled India into an elite group of five other nations (USA, erstwhile USSR, France, China and Japan) with similar capabilities.

It is expected to be used in the upper third stage of the Geostationary Satellite Launch Vehicle (GSLV).


What is Cyclone?

A cyclone is a low pressure area in the atmosphere in which the winds spiral inward in an anticlockwise direction. All cyclones are characterized by having an atmospheric pressure lowest at the centre and winds spiraling in towards this low pressure central zone called the ‘eye’. Cyclones are usually characterized by gusts of winds which may even go up to 250 kilometres/hour. In addition they are also accompanied by heavy rain. Along coastal areas they sometimes produce high tidal waves. In the southern hemisphere the winds blow in a clockwise direction. Cyclones are called hurricanes if they form in the West Indies and typhoons if they form in western Pacific.

In India a large number of cyclones originate in the Bay of Bengal and occasionally cause large-scale devastation on the eastern coast. The 1970 cyclone which hit the coast of Andhra Pradesh killed thousands of people and devastated property worth crores of rupees.


What is Detergents?

Detergents are synthetic chemical salts which change the surface property of water and which are used as cleaning agents. Detergents contain one or more chemicals called surfactants, which reduce the surface tension of water by weakening the forces between water molecules. This enhances the cleaning action of water. A detergent molecule has two different parts. One part is hydrophilic (water-loving head) while the other is hydrophobic (water-hating tail). When soiled clothes are put in a detergent solution, water-loving head remains in water while the tail attaches to the grease or oil holding the dirt particles on the soiled material. Rubbing helps in breaking up the dirt. In this way the dirt particles are dislodged from the surface of the material and drawn into the wash water. After the dirt particles are suspended in water, a thin layer of surfactant remains around the particles keeping them separated. This prevents the dirt from settling on the washed material again. This is how detergents help in cleaning.

The common soap (sodium salt of fatty acid) is one of the oldest detergents but it is relatively weak. Synthetic detergents are stronger than soap and give lather even in hard water. 

What is Dialysis?

Dialysis is a process of separating dissolved substances from a solution using a semi-permeable membrane which allows only some dissolved substances to pass through. Many substances such as cell walls and cellophane act as semi-permeable membranes.

Dialysis is used to remove waste-products from the blood of patients with impaired kidney function. Accumulation of waste products especially urea, in the blood can prove fatal.

Dialysis of blood is carried out using a dialysis machine. Blood drawn from the artery in the forearm of the patient is passed through a semi-permeable membrane. The tubing is placed in a solution called dialysis fluid. Since the blood has a high concentration of impurities compared to the dialysis fluid, a concentration gradient builds up. This results in a flow of soluble impurities from the blood into the dialysis fluid. This continues till the concentrations on each side of the membrane are balanced. To prevent clotting of blood in the dialysis machine, the anti-clotting substance heparin is used.


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What is DTP?

DTP or Desk-top Publishing is a method of designing, editing and laying out a publication electronically using a personal computer and word processing, graphics and page layout software. This term, DTP, was first coined by Paul Brainerd, a British pioneer in this field.

In a DTP process, whatever be, the matter or layout of a page, it is composed electronically and stored in the computer with the help of a page making software. Corrections of any type or changes can be easily done any number of times on the computer and the desired output is then obtained from a laser printer on paper. The camera ready text matter is then converted into photographic film (negative or positive) from which plates are made for printing. In newspaper publishing, it provides for incorporation of text, as it arrives by e-mail, directly into the pages being prepared. DTP is a versatile technology for applications in the advertising, designing and publishing business.


What is E-mail?

E-mail is the short form for electronic mail, which is based on the use of computers for the transmission of messages rather than through the postal system. The e-mail system connects a network of personal computers (PC) spread over hundreds of locations within a country or across the globe. A PC is set-up as a message server in the system. The users at other PCs can link up with the server at any time to receive and transmit messages.

Each user of the e-mail system is allotted a code number or address in the e-mail directory. To send a message, a user has to “key-in” the message in his PC along-with the directory numbers allotted to him and the receiver of the message. The sender can indicate if the message is confidential or universal and also set a time limit for its retention. The receiver, on receiving the message at his computer terminal, can get it printed on paper.

 The main advantages of e-mail are that it cuts down the delay involved in postal transmission of messages. Moreover, messages can be sent at any time of day or night which are stored and can be retrieved by the recipient at his or her convenience. Besides once the contact between the transmitter and receiver PCs is established e-mail requires only a few minutes time to transmit even a bulky message. 

What is El Nino?

The El Nino is a narrow current of warm water that appears off the coast of Peru sometime in December-January and which lasts till March. The name literally means ‘The Child’ and refers to the Child Christ, apt because the appearance of the current coincides with Christmas. As it flows southward along the west coast of South America, it warms the cold waters of the coast of Ecuador and Peru.

El Nino was first recorded as early as in 1726 and it has returned on an average of once every four years. El Nino is believed to be related to a shift in air movements over the tropical Pacific Ocean. Changes in wind direction bring about changes in the circulation and temperature of the oceans. This in turn further disrupts ocean currents and air movements.

A powerful El Nino in 1982 and 1983 caused severe drought in Australia and Indonesia. It also caused storms in California and rains and floods in Ecuador and Peru. The El Nino effect also profoundly affects the Indian monsoons.


What is Endoscopy?

Endoscopy is a harmless and painless method of diagnosing diseases of any of the hollow organs of the body (like throat, stomach or intestine) by looking directly into the affected organ using a probe called endoscope. It is a hollow metallic tube fitted with a light source and a viewing system.

Modern endoscopes make use of flexible bundles of optical fibres both for transmitting light to the organ and transmitting the image to the eyepiece outside for viewing.

Since the endoscope gives a direct view of the affected body parts, patients need not go for complicated investigations.

Advanced endoscopes may have surgical attachments to carry out minor operations or biopsy.



What is FAX?

Fax or facsimile is a device used for transmission of a written document, photograph, map or any other graphic material electronically. It is one of the variants of e-mail. For transmission the original document is placed in the facsimile or fax machine which scans the document and converts the written or graphic information into electronic signals and establishes a link-up with a similar receiving fax machine at the receiving end. The receiving fax reconverts the electronic signals into written or graphic form. As the sending machine scans the documents, the receiving machine reproduces the scanned image which is an exact duplicate of the originals. A typical fax machine can transmit a document of A-4 size in less than a minute over thousands of kilometres. Since fax operates through the normal telephone lines, the fax number is usually a telephone number. Also the same STD and ISD codes are used for sending a fax to another city or another country. The document is scanned page-by-page in the fax machine. Like the e-mail, fax communication eliminates the postal delay and is very convenient for communication between persons located in different time zones, but it costs more than the e-mail. 

Why is C. V. Raman considered to be a scientist par excellence?

Sir C. V. Raman is best known for his work in the field of light scattering. Raman was intrigued by the blue colour of glaciers and the Mediterranean Sea and wanted to unravel the mystery as to why water, a colourless liquid, appeared blue to the eyes.

    Thus, he began a series of experiments on the scattering of light which ultimately led to what came to be known as the ‘Raman Effect’. Raman also discovered that when light interacts with a molecule, the light can donate a small amount of energy to te molecule. As a result of this, the light changes its colour and the molecule vibrates.

   The change of colour can act as a ‘fingerprint’ for the molecule. Today, Raman spectroscopy, which relies on these ‘fingerprints,’ is used in laboratories all over the world to identify molecules and to detect disease such as cancer.

     Sir C. V. Raman received the Nobel Prize for Physics in 1930. He was the first Indian to win the Nobel Prize for Physics, and is considered to be a scientist par excellence.

Why Srinivasa Ramanujan is considered a mathematical genius?

Srinivasa Ramanujan was, without doubt, a mathematical genius. Without any formal training in the subject, he made significant contributions to the theory of numbers, investigation of elliptical functions, infinite series, continued fractions, and Mock theta functions.

    Ramanujan showed a natural inclination towards mathematics when he was ten years old. By age 11 he had more mathematical knowledge than two college students who were lodgers at his home. He completely mastered advanced trigonometry by the age of 13, and discovered sophisticated theorems on his own.

   His memory for mathematical formulae and constants seems to have been boundless- he amazed classmates with his ability to recite the values of irrational numbers to as many decimal places as they asked for.

   Ramanujan went to Cambridge in April 1914, thanks to the help of Prof. G. H. Hardy. Two years later, he was awarded the equivalent of a PhD. for his work. The notebooks he had brought from India were filled with thousands of identities, equations and theorems which he had discovered for himself.

   In 1918 Ramanujan became the first Indian Mathematician to be elected a Fellow of the British Royal Society.

What were Sir Jagadish Chandra Bose’s contributions?

Sir Jagadish Chandra Bose is one of the most famous among Indian scientists. He was a physicist, biologist, biophysicist, botanist and archaeologist, as well as a writer of science fiction.

  Bose proved by experimentation that both animals and plants share much in common. He demonstrated that plants are also sensitive to heat, cold, light, noise and various other external stimuli.

   Bose built a very sophisticated instrument called Crescograph which could record and observe the minute responses of plants to external stimulants. He authored two illustrious books and extensively researched the behavior of radio waves.

       Bose devised another instrument called ‘Coherer’. In 1917, he founded the Bose Institute, and dedicated it to the promotion of scientific studies in India.

Why is Aryabhata considered to be a giant among mathematicians?

Aryabhata was a great mathematician and astronomer in Ancient India. He wrote many mathematical and astronomical treatises. His chief work was the ‘Ayrabhatiya’ which was a compilation of mathematics and astronomy.

   Ayrabhatiya covers several branches of mathematics such as algebra, arithmetic, plane and spherical trigonometry. Included in it are theories on continued fractions, sum of power series, sine tables, and quadratic equations.

  Aryabhata also did a considerable amount of work in astronomy. He knew that the Earth is rotating on an axis around it. He discovered the position of nine planets and stated that these also revolved around the sun.

    Aryabhata stated that the correct number of days in a year is 365. He was the first person to mention that the Earth was not flat but, in fact spherical shape. This great man has been honored in many ways. The first Indian satellite was named ‘Aryabhata’. A lunar crater and Indian research centre also bear his name.