With reference to street-lighting, how do sodium lamps differ from LED

With reference to street-lighting, how do sodium lamps differ from LED lamps?

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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.

3 only

2 only

1 and 3 only

1, 2 and 3

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Answer is Wrong!

This question was previously asked in

UPSC IAS – 2021

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Statement 1 is correct. Traditional sodium lamps (like high-pressure sodium lamps) emit light omnidirectionally (in all directions), requiring reflectors to direct light downwards onto the street. LED lamps, by contrast, are inherently directional light sources, meaning they emit light primarily in a specific direction (forward). This directional nature allows for more efficient targeting of light where needed. Statement 2 is incorrect. LED lamps generally have a much longer lifespan (typically 50,000 to 100,000+ hours) compared to sodium lamps (typically 20,000 to 30,000 hours). Statement 3 is correct. High-pressure sodium lamps produce a predominantly yellow-orange light, resulting in poor color rendering (objects appear unnatural or monochrome). LED lamps can produce white light with various color temperatures and offer significantly better color rendering index (CRI), which improves visibility, recognition of objects and colors, and safety under street lighting.

– Sodium lamps emit light omnidirectionally, while LEDs are directional.
– LEDs have a significantly longer lifespan than sodium lamps.
– Sodium lamps provide poor color rendering (monochromatic light), while LEDs offer much better color rendering.

LED street lights also offer advantages in terms of energy efficiency (lower power consumption), instant on/off capability, dimmability, and environmental benefits (no mercury). These factors have led to a widespread shift from sodium vapor lamps to LED technology for street lighting globally.

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