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.

Statements 1 and 3 are correct; statement 2 is not. 1. **Correct.** Sodium-vapour lamps emit light omnidirectionally (≈360°), so a large fraction of the light is wasted upwards or sideways and has to be redirected with reflectors. LEDs are inherently directional sources (typically a forward beam of ≈180° or less), which makes them more efficient for street lighting where light is needed only on the road surface. 2. **Incorrect.** LED street lights have a much longer rated life — typically 50,000–100,000 hours — than high-pressure sodium lamps, which last roughly 12,000–24,000 hours. Sodium lamps therefore have a *shorter* life span than LEDs, not longer. 3. **Correct.** Low/high-pressure sodium lamps emit an almost monochromatic yellow-orange light (very poor colour rendering, CRI close to zero or low double digits). White LEDs offer a much broader, tunable spectrum and high colour rendering, giving significant colour-recognition advantages in street lighting. Hence only 1 and 3 are correct, and the answer is C.