microphone is a device which converts sound waves into electrical signals. These signals can then be broadcast through the air or sent over to distant points, where they can again be converted back into sound. Microphone can be divided into two groups depanding upon how they respond to sound waves…..

The term LPG Liquified Petroleum Gas. LPG is commonly used for domestic cooking purpose. It is supplied in gas cylinders that need to be replaced when their fuel contents are consumed. The supply in gas cylinders contains a mixture of liquified butane and iso-butane under pressure…..

We all know that electricity travels from one place to another through metallic wires. Light can also travel through wires but these wires are not made of metals. They are made of glass or plastic. Light carrying wires are extremely thin and are called optical fibres…..

For thousands of years many scientists groped in dark to understand the true nature of light. The ancient Greeks belived that light consisted of rays of matter given out by whatever object was being looked at. Plato and his followers belived that it was a mixture of different matters coming from the sun…..

Liquid crystals are of two types: thermotropic liqid crystals prepared by heating the substance and lyotropic liquid crystal made by mising two or more compounds. Some of the imporatant liquid crystals that belong to the first category are p-azoxyanisole cholesteryl nonanoate and p-n octyloxybenzoic acid…..

All men women and children, who have weak eye-sight, use spectacles. Scientist have developed spectacles that help in seeing both the near distant object clearly. The history of spectacles was started some 700 years ago…..

Hardness is a characteristic property of the solid objects. It is measured by the resistance which the body offers to anything which tends to scratch it. The hardness of the various materials is measured either on the mohs scale or the knoop scale…..

Heavy water was discovered by harold Clayton Urey an American chemist in 1931. He was awarded the Nobel Prize in 1934 for this discovery. Naturally occurring hydrogen contains 99.985% of protium, about .015% deuterium and about 1 part in 1017 tritium…..

Wine is probably the first type of hard drink to have come into existence. Archaeological evidence suggests that wine making began in the middle-east over 10,000 years ago, and gradually spread westward to the mediterranean countries and finally into Europe……

Our earth reflects a lot of energy back into the atmosphere. But presence of heavy carbondioxide in the atmosphere prevents some of this heat escaping just as a glass or plastic sheet stops escaping heat from the so called “Greenhouse” used to protect groing plants…..