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.

[UPSC Civil Services Exam – 2021 Prelims]

(a) 3 only

(b) 2 only

(c) 1 and 3 only

(d) 1, 2 and 3

Answer: (c)        

Explanation:

• Sodium lamps produce light in 360 degrees but it is not so in the case of LED lamps. LED lamps have 180-degree bulb angle to preserve light efficiency and allow for target lighting over areas. Statement 1 is correct.
• As street lights, sodium lamps have on an average shorter lifespan than LED lamps. High Pressure Sodium lamps tend to have a lifespan averaging 24,000 hours. Whereas, LED lamps lifespan ranges from 25,000 to 200,000 hours. Statement 2 is incorrect.
• Sodium lamps emit a nearly monochromatic visible light spectrum, resulting in a warm yellow glow. Conversely, LED lamps are superior in street lighting due to their various color options, providing better lighting solutions compared to High Pressure Sodium lamps. Statement 3 is correct.