Prelims 2021

Q. 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 a longer lifespan 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.
a) 3 only
b) 2 only
c) 1 and 3 only
d) 1, 2 and 3
Correct Answer: c) 1 and 3 only

Question from UPSC Prelims 2021 GS Paper

Explanation : 

Street Lighting: Sodium vs. LED Lamps

The comparison between sodium lamps and LED lamps for street lighting involves several factors, including the direction of light emission, lifespan, and color spectrum. Here’s a detailed explanation:

Direction of Light Emission

Sodium lamps are known for their 360-degree light emission, which requires the use of reflectors in streetlights. In contrast, LED lamps emit light directionally, enhancing their efficiency in street lighting applications.

Lifespan Comparison

LED lamps boast a longer lifespan than sodium lamps. While sodium lamps can last up to 24,000 hours, LEDs can last up to 100,000 hours, offering greater durability and cost-effectiveness over time.

Color Spectrum and Visibility

Sodium lamps produce a nearly monochromatic yellow light with poor color rendering, making it difficult to distinguish colors. LED lamps, however, provide a broad spectrum of visible light with excellent color rendering, which significantly improves night-time visibility and color distinction.

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