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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A hard Science & Technology multiple-choice question from UPSC Prelims 2021. Attempt it above, then check the correct answer and detailed explanation below.
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Correct answer: C. 1 and 3 only
Statements 1 and 3 are correct — sodium lamps emit light in all directions (360 degrees) while LEDs are directional, and sodium light is almost monochromatic whereas LEDs give better colour rendering. Statement 2 is wrong — LEDs have a longer lifespan than sodium lamps.
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