Question

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 1

Correct option is (c) 1 and 3 only

• Sodium lamps provide 360 degree light emitting. Whereas, LED lights tend to direct light downward, rather than a full 360 degrees. → #1 is right.
• HPS Lights have good lifespans - around 14,000 hours-though this is significantly less than LEDs. LEDs last longer than any light source commercially available on the market. → #2 is wrong.
• Monochromatic light means that the light has a single wavelength. The LED light is not monochromatic because it is made up of different wavelengths, therefore is polychromatic. Often, a combination of wavelengths is used to create different colors. → #3 is right.