Why won’t two small sodium lamps, held close together, produce an interference pattern on a distant screen? what if the sodium lamps were replaced by two laser pointers held close together?

Two sodium lamp not produce visible interference but two lasers with sufficient thin opening may produce interference pattern.

Explanation:

Two sodium lamp light wave interfere on distant screen but cannot be seen because so many couples of waves are on that screen. Thus fringes of all of them become totally invisible.

Two thin laser pointers are good substitute for Youngs double slit experiment but in front of both laser beam you have to put thin slits to observe the fringes.

b.

explanation:

a electromagnetic waves