With reference to street-lighting, how do sodium lamps differ from LED lamps?
- 1.Sodium lamps produce light in 360 degrees but it is not so in the case of LED lamps.
- 2.As street-lights, sodium lamps have longer life span than LED lamps.
- 3.The spectrum of visible light from sodium lamps is almost monochromatic while LED lamps offer significant colour advantages in street-lighting.
Select the correct answer using the code given below.
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Answer: C. Statement 1 is correct: sodium lamps emit light all around (360 degrees), while LEDs are directional. Statement 2 is wrong: LEDs last much longer than sodium lamps. Statement 3 is correct: sodium lamps give a near single-colour yellow light, while LEDs offer better colour rendering. So 1 and 3.
Watch for: Older sodium lamps are seen as rugged, but LEDs clearly have the longer life.
Why the other options are wrong
- A. Wrong because statement 1 is also correct.
- B. Wrong because LEDs, not sodium lamps, last longer.
- D. Wrong because statement 2 is false.
Source to check: Bureau of Energy Efficiency / EESL Street Lighting National Programme documents
Answer from the official UPSC key. Written and fact-checked by AI against the official key. Spotted a mistake? Report it.