Assume that the maximum aperture of the human eye, D, is approximately 8 mm and the average wavelength of visible light, λ, is 5.5 x 10-4 mm.

a. Calculate the diffraction limit of the human eye in visible light.
D = 8 mm = 0.008 m
λ = 5.5 x 10-4 mm = 5.5 x10-7 m
θ = (2.06 x 105) . ( (5.5 x 10-7) / (0.008) ) = 14.1625 arcseconds

b. How does the diffraction limit compare with the actual resolution of 1-2 arcminutes (60- 120 arcseconds)?

c. To what do you attribute the difference?

I know the answer for part a but i didn't understand b and c