The rayleigh criterion?

Question

The limit to the eyes acuity is actually related to diffraction by the pupil. What is the angle between two just revolvable points of light for a 3.00 mm diameter pupil, assuming an average wavelength of 550 nm? What is the greatest possible distance a car can be from you if you can resolve its two headlights given they are 1.30 m apart? What is the distance between two just resolvable points held at arms length (0.800m) from your eye?

Answer 1

The Rayleigh criterion for a circular aperture is sinθ = 1.22λ/D. (See the ref.) Given validity of a small angle approximation (D >> λ) this can be simplified to θ = x/d = λ/D, where x = minimum resolvable separation and d is distance.