Question

What are coherent sources? Why are they necessary for observing a sustained interference pattern?

Hint:

Coherent sources produce waves that are in phase or maintain a constant phase difference. This is essential for stable and clear interference patterns.

Answer 1

Coherent sources are sources of light (or other waves) that emit waves with a constant phase difference and the same frequency. These sources produce waves that maintain a consistent phase relationship over time. Coherence is crucial for producing stable interference patterns, as the phase difference between the waves needs to remain constant for constructive and destructive interference to occur.
In interference experiments, coherent sources ensure that the waves from each source interfere in a sustained manner, producing a stable pattern of bright and dark fringes.