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.

1. Statement 1 is correct. Sodium lamps (like High-Pressure Sodium - HPS) typically use an arc tube that emits light radially, essentially in 360 degrees. This requires reflectors within the fixture to direct the light downwards. LED lamps are inherently directional, emitting light in a specific direction (e.g., 180 degrees or less), which is more efficient for applications like street-lighting as less light is wasted. 2. Statement 2 is incorrect. LED lamps generally have a significantly longer life span (often 50,000-100,000 hours or more) compared to sodium lamps (HPS lamps typically last around 24,000 hours). 3. Statement 3 is correct. Low-Pressure Sodium lamps produce an almost monochromatic yellow light. High-Pressure Sodium lamps produce a broader spectrum but still have poor colour rendering (yellowish/orange hue). LED lamps can be designed to produce light across a wide range of colour temperatures and offer much better colour rendering (ability to show colours accurately), which is a significant advantage for visibility and safety in street-lighting. Therefore, statements 1 and 3 are correct.