Prelims 2011 · archive
EasyWhat 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 semiconductor material.
- 2.The average lifespan 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?
Answer & explanation
Answer: (c) 1 and 3 only
Statements 1 and 3 are correct. A CFL is a fluorescent lamp: mercury vapour gives off ultraviolet light, and a phosphor coating turns it into visible light. An LED makes light in a semiconductor chip. For the same light, an LED uses about half the power of a CFL and lasts several times longer, so statement 2 is wrong.
- ✓ 1. In a CFL, an electric discharge excites mercury vapour, and the phosphor coating inside the tube converts the resulting ultraviolet radiation into visible light. An LED produces light directly inside a semiconductor chip, with no gas or mercury.
- ✗ 2. The US Department of Energy puts a typical CFL at 8,000 to 10,000 hours. LED lamps last several times longer than that. So an LED outlasts a CFL, not the other way round.
- ✓ 3. A 7W LED bulb gives the same light as a 14W CFL, a saving of about 50% energy compared with the CFL. A CFL is therefore less energy-efficient than an LED.
Remember · Compared with a CFL, an LED lamp is a semiconductor device that uses about half the power for the same light and lasts several times longer. A CFL uses mercury vapour and phosphor.
Sources
- US Department of Energy – LED Basics (lifetime of LED vs CFL) ↗ “A typical incandescent lamp lasts about 1,000 hours; a comparable CFL, 8,000 to 10,000 hours; and the best linear fluorescent lamps, more than 30,000 hours.”
- PIB, Ministry of Power – UJALA: 10 Years of Energy-Efficient Lighting ↗ “A 7W LED bulb provides the same amount of light as a 14W Compact Fluorescent Lamp (CFL) and a 60W Incandescent Lamp (ICL), thereby saving nearly 90% energy compared to ICLs and 50% in the case of CFLs.”
Question: UPSC Civil Services (Preliminary) 2011, General Studies paper. Explanation: Minimalist IAS, checked 25 Oct 2026 (how we verify). ·