There is a telescope whose objective has a diameter `D = 5.0 cm`. Find the resolving power of the objective and the minimum separation between two points at a distance `l = 3.0km` from the telescope, which it can resolve (assume `lambda = 0.55 mu m)`.

Explanation

Resolving power of the objective
`=(D)/(1.22 lambda) = (5 xx 10^(-2))/(1.22 xx 0.55 xx 10^(-6)) = 7.45 xx 10^(4)`
Let `(Deltay)_(min)` be the minimum distance between two points at a distance of `3.0km` which the telescope can resolve. Then
`((Deltay)_(min))/(3 xx 10^(3)) = (1.22 lambda)/(D) = (1)/(7.45 xx 10^(4))`
or `(Deltay)_(min) = (3 xx 10^(3))/(7.45 xx 10^(4)) = 0.04026m = 4.03cm`.