With reference to street-lighting, how do sodium lamps differ from LED lamps?<br/>1. Sodium lamps produce light in 360 degrees but it is not so in the case of LED lamps.<br/>2. As street-lights, sodium lamps have longer life span than LED lamps.<br/>3. The spectrum of visible light from sodium lamps is almost monochromatic while LED lamps offer significant colour advantages in street-lighting.<br/><br/>Select the correct answer using the code given below.

1. Correct. Sodium vapour lamps emit light in nearly all directions (360°), so reflectors are needed; LEDs are inherently directional and do not emit uniformly in 360°.

2. Incorrect. In street-lighting, LEDs generally have a longer service life than sodium lamps and also maintain efficiency better over time.

3. Correct. Sodium lamps, especially low-pressure sodium lamps, produce almost monochromatic yellow light with poor colour rendering; LEDs provide much better colour rendering and spectrum control.

Hence, statements 1 and 3 only are correct.