Correct Option
Statements 1 and 3 are correct.
Statement 1: Sodium lamps emit light omnidirectionally (360 degrees). In contrast, LED lamps are directional light sources, emitting light in a focused pattern, typically downwards. This characteristic of LED lamps reduces light spill and improves efficiency in street lighting applications.
Statement 3: Sodium lamps, particularly low-pressure sodium lamps, produce light that is almost monochromatic, primarily in the yellow-orange spectrum. This results in poor colour rendering. LED lamps, however, emit a broader spectrum of visible light, offering superior colour rendering and enhanced visibility, which is advantageous for street-lighting.
Incorrect Options
Statement 2 is incorrect. LED lamps possess a significantly longer operational lifespan compared to sodium lamps. High-pressure sodium (HPS) lamps typically last between 14,000 and 24,000 hours, whereas LED streetlights can function for 50,000 hours or more, contributing to their long-term cost-effectiveness.