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Q63 (IAS/2011) Science & Technology › New Materials, Energy & Environment-linked Tech › Efficient lighting technologies Answer Verified

What is the difference between a CFL and an LED lamp ? 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 is compared to an LED lamp. Which of the statements given above is/ are correct?

Result
Your answer: —  Â·  Correct: C
Explanation

Statement 1 is correct as CFLs operate by passing an electric current through mercury vapour to produce ultraviolet light, which then excites a phosphor coating to emit visible light. In contrast, LEDs produce light by passing current through a semiconductor material. Statement 2 is incorrect because LEDs have a significantly longer lifespan, typically lasting between 15,000 to 50,000 hours, whereas CFLs generally last only 7,000 to 15,000 hours [1]. Statement 3 is correct because LEDs are more energy-efficient than CFLs; LEDs use approximately 50% less energy than fluorescent lights and convert up to 90% of their energy into light, while CFLs lose more energy as heat [1]. Therefore, only statements 1 and 3 are accurate descriptions of the differences between these lighting technologies.

Sources

  1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 11: Light: Shadows and Reflections > SCIENCE AND SOCIETY > p. 154
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