Assuming human pupil have a radius of 0.25 cm and a comfortable viewing distance of 25 cm. The minimum separation between two objects that human eye can able to  resolve at 500 nm wavelength is

minimum angle to resolve by any optical instrument is θ=1.22λDD = diameter of human eyeand minimum distance between two points will be θ x, where x is the distance between the object and eye.θ x=1.22λDx =1.22×5×10-7×25×10-22×0.25×10-2=30×10-6