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.
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.
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.
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 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.
