In the printed figure, the lines are separated by 2 mm. Viewed at a distance, the two patterns look identical, but as you approach them, there is a point at which you can barely resolve the lines and tell the difference between the two images. From this distance L, you can calculate the angular resolution of your eyes:
angular resolution = (2 mm)/L (in radians).
Classroom demonstration: Hold up the figure and ask who can see the lines in one of the patterns. Usually no one beyond 4 meters will raise their hands. (This works best in a classroom which is 8 meters or more deep.) Using the above equation, L = 4 m corresponds to an angular resolution of 0.03 degrees.
The diffraction limit of the eye can be calculated using Rayleigh's criterion:
angular resolution = (1.22)(lambda)/D,
where lambda is the wavelength of light (on the average, about 550 nm) and D is the diameter of the eye's pupil, which is about 5 mm indoors. This calculation results in an angular resolution of 0.008 degrees. If your eyes could resolve images at the diffraction limit, you could resolve the lines in the printed pattern at a distance of 15 m!