Question

how can u obtain a point of source of light ?

Answer 1

if we make the lines falling on the concave mirror parallel to the principal axis then that rays will meet at focus and hence we can obtain a source of light on a point.

Answer 2

HEY MATE HERE IS YOUR ANSWER ♥♥♥

depends the size of the point and the light emission cone you consider.

A single atom can emit a single photon in a random direction. A LED or fiber optics can emit a narrow cone of light from a few squared microns surface. A distant star can be considered as a point from here …

HOPE THIS HELPS YOU ♥♥♥