You look at an eye chart 3 meters away. What is the smallest size of the letter you should see
(assuming the pupils’ diameter is 4mm and light wave length is 500nm)? Will this size increase or
decrease if you put a hole smaller than the pupil in front of
your eye?

Question

You look at an eye chart 3 meters away. What is the smallest size of the letter you should see
(assuming the pupils’ diameter is 4mm and light wave length is 500nm)? Will this size increase or
decrease if you put a hole smaller than the pupil in front of
your eye?

anonymous · Answer

The equation that gives minimum resolution for a diffraction limited system (which the eye is in this problem) is as follows:$$x=1.22\frac{  \lambda }{ d }$$where x is the resolution; λ is the wavelength; and d is the aperture diameter.  Now, what happens to x, the resolution, as d goes down?