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 longer life span 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.
- 3 only
- 2 only
- 1 and 3 only
- 1, 2 and 3
Explanation
Statement 1 is correct
- Sodium lamps, including both low-pressure and high-pressure types, emit light in a 360-degree pattern. This means they produce light in all directions around the lamp. To use them effectively in street lighting, reflectors are typically required to direct the light downward onto the road and sidewalks. This omnidirectional emission can lead to some inefficiencies, as a portion of the light may not be effectively used for illuminating the street.
- LED lamps are designed to emit light in a specific direction, usually in a 180-degree arc or less. This directional nature allows LED lamps to focus light precisely where it is needed without additional reflectors. This design reduces light pollution and improves the efficiency of street lighting by directing more light onto the street and less into unintended areas like the sky or surrounding spaces.
Statement 2 is incorrect
- LED lamps have a longer lifespan compared to sodium lamps. LED lamps are known for their durability and efficiency, often lasting longer than traditional sodium lamps.
Statement 3 is correct
- Sodium lamps, particularly low-pressure sodium lamps, produce light that is almost monochromatic, primarily in a yellow-orange hue. High-pressure sodium lamps offer a somewhat broader spectrum but still have limited color rendering capabilities. This monochromatic light can make it difficult to distinguish colors and affects visibility, making the environment appear dim and less natural. Color Rendering Index (CRI) of sodium lamps is low, meaning they do not render colors accurately compared to other light sources. This can be a disadvantage for applications where color differentiation is important, such as in traffic signaling or detailed visual tasks.
- LEDs offer a broad spectrum of light and are available in various color temperatures, ranging from warm white to cool white. This broad spectrum allows LEDs to provide better color rendering, making colors appear more natural and true to life. The high CRI of LEDs improves visibility and safety by making it easier to distinguish between different colors and details. LED street lights come in different color temperatures, allowing for customization based on specific lighting needs and preferences.
