UPSC Government Jobs Exams

What is the difference between a CFL and an LED lamp? [UPSC 2011 (CS-P)]
1. To produce light, a CFL uses mercury vapour and phosphor while an LED lamp uses semi-conductor material.
2. The average life span of a CFL is much longer than that of an LED lamp
3. A CFL is less energy-efficient as compared to an LED lamp.
Which of the statements given above is/are correct?

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UPSC Other Question
What is a zoom lens? Which features of some species of blue – green algae helps promote them as bio-fertilizers? [UPSC 2010 (CS-P)]

They convert atmospheric methane into ammonia which the crop plants can absorb readily.
They induce the crop plants to produce the enzymes which help convert atmospheric nitrogen to nitrates.
They have the mechanism to convert atmospheric nitrogen into a form that the crop plants can absorb readily.
They induce the roots of the crop plants to absorb the soil nitrates in larger quantities.