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 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.

[A] 3 only

[B] 2 only

[C] 1 and 3 only

[D] 1, 2 and 3

Answer: C
Notes:

Why this Question) Government focus on LED lights (Ujala Yojana); environment friendly. 

 

Ans) c 

Exp) Option c is correct.  

Statement 1 is correct. 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 2 is incorrect. 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 3 is correct. The spectrum of visible light from sodium lamps is almost monochromatic as they are known for their warm yellow glow. On the other hand, LED lamps offer significant colour advantages in street-lighting. LEDs offer variety of colour options providing better lighting solutions than High Pressure Sodium counterpart. 

Source) https://www.homelectrical.com/advantages-led-vs-high-pressure-sodium-area-lights.6.html  

 Subject) Science