Solution

Past exam of the mathematics course of the University of Cambridge / 2006 / iii / Paper 72 / 3 / iii / Solution

Past exam of the mathematics course of the University of Cambridge / 2006 / iii / Paper 72 / 3 / iv / e / Solution

A point-like astronomical source has an angular extent negligible for the calculation or measurement being considered. The ideal mathematical limit concentrates its luminosity at one source-plane position. In <gravitational lensing>, this approximation permits divergent formal magnifications on a caustic; a finite source averages the magnification over its emitting area. An unresolved source need not have negligible size compared with the lens's caustic scale.

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 Incoming links: Point-like astronomical source