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.

Statement 1 is correct: Sodium vapor lamps emit light omnidirectionally (360 degrees), requiring reflection and redirection, leading to inefficiency. LEDs emit light directionally (over 180 degrees), minimizing the need for redirection and reducing losses.

Statement 2 is not correct: LEDs have a significantly longer lifespan than sodium lamps. LED lifespan can exceed 100,000 hours, more than 4 times that of sodium lamps. This results in lower maintenance and replacement costs for LEDs.

Statement 3 is correct: Sodium lamps produce a nearly monochromatic light (yellow-orange), causing objects of other colors to appear as shades of gray. LEDs offer a broad spectrum of color rendering index (CRI), generally ranging from 65-95, providing significant color advantages in street lighting.

Hence, statements 1 and 3 are correct.

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