UPSC Prelims 2010·GS1·science-and-technology·science and technology

Indiscriminate disposal of used fluorescent electric lamps causes mercury pollution in the environment. Why is mercury used in the manufacture of these lamps?

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  1. AA mercury coating on the inside of the lamp makes the light bright white
  2. BWhen the lamp is switched on, the mercury in the lamp causes the emission of ultra-violet radiationsCorrect
  3. CWhen the lamp is switched on, it is the mercury which converts the ultra-violet energy into visible light
  4. DNone of the statement given above is correct about the use of mercury in the manufacture of fluorescent lamps

Explanation

The correct answer is B because mercury plays a critical role in the gas discharge process of a fluorescent lamp. When the lamp is switched on, an electric current passes through the mercury vapor, exciting the mercury atoms. These excited atoms then release energy in the form of ultraviolet radiations. These ultraviolet rays hit the phosphor coating on the inside of the glass tube, which then glows to produce visible light. Therefore, mercury is essential for generating the initial ultraviolet radiation required for the lamp to function.
science-and-technology: Indiscriminate disposal of used fluorescent electric lamps causes mercury pollution in the environment. Why is mercury u

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