Physics
Tungsten is used for the manufacture of the filament of an electric bulb, because

It is a good conductor
It has a very high melting point
It is economical
It is malleable

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Physics
Holography is a technique of

Recording a permanent, sharp two diimensional black and white or multicolour photograph
Recording a permanent three dimensional multicolour photograph
Recording a permanent three dimensional black and white photograph
Recording a permanent three dimensional photograph of a given single colour or a multicolour

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Physics
Lightning is produced when

Water vapour produces electricity in the clouds
Strong opposite charges in different clouds break down the resistance offered by the intervening air
Clouds strike against impurities in air and the friction burns up these impurities
Similar charges of electricity rush towards each other and then get repelled

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