Whaat is meant by temporal and spatial coherence and why are they necessary condition for interference? We intend to produce interference pattern using Young doble slit experiment with light of mean wavelength 500 nm and line width 2.5x10-3 nm at what optical path length difference do you expect the fringe to vanish?

Whaat is meant by temporal and spatial coherence and why are they necessary condition for interference? We intend to produce interference pattern using Young doble slit experiment with light of mean wavelength 500 nm and line width 2.5x10-3 nm at what optical path length difference do you expect the fringe to vanish?