for images of two wave sources to be just resolved the maximum of one diffraction pattern is coincident with the first minimum of the other. (d)

The minimum anglular separation in the diffraction pattern,

for two objects to be resolved is given by

, for single slits of width

*b*;

, for circular apertures of diameter

*b.*

If two objects at a distance r from the pupil/telescope, separated by distance s, are just resolved then, since

, we can write

which can be used to solve typical problems on resolution.