Question
UPSC Prelims 2021 Question:
With reference to street - lighting, how do sodium lamps differ from LED lamps?
- Sodium lamps produce light in 360 degrees but it is not so in the case of LED lamps.
- As street -lights, sodium lamps have a longer lifespan than LED lamps.
- 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.
Answer (Detailed Solution Below)
Detailed Solution
Explanation:
- The key difference between Sodium lamps and LED lamps are as follows:
|
Parameter |
Sodium Lamp |
Led Lamp |
|
Starting time |
Sodium Lights have a long warm-up time, usually around 15-20 minutes. |
LED fittings are instantly at full output. |
|
Directionality |
Sodium lights are omnidirectional, i.e, they produce light in 360 degrees. |
LED lamps produce light in 180 degrees. This is typically an advantage because light is usually desired over a target area rather than all 360 degrees around the bulb. So, statement 1 is correct. |
|
Lifetime |
Sodium Lamps have good life spans – around 14,000 hours – though this is significantly less than LEDs. |
LEDs' lifespan is typically 40,000 - 60,000 Hours. So, statement 2 is not correct. |
|
Colour and its associated wavelength |
Lights have a very narrow color spectrum (monochromatic), limited to warm deep yellow light. |
LEDs are available in a wide range of colour temperatures (ranging from 'warm white' to 'daylight'). So, statement 3 is correct. |
Therefore, option (3) is the correct answer.
Subject: Science & Technology | Miscellaneous
Last updated on June, 2026
