1. The problem statement, all variables and given/known data Once dark adapted, the pupil of your eye is approximately 7 mm in diameter. The headlights of an oncoming car are 120 cm apart. If the lens of your eye is diffraction limited, at what distance are the two headlights marginally resolved? Assume a wavelength of 600 nm and that the index of refraction inside the eye is 1.33. 2. Relevant equations [tex]\theta[/tex]min=1.22[tex]\lambda[/tex]/D where [tex]\lambda[/tex] is the wavelength, D is the diameter of the lens, and theta min is the angular resolution of a lens. 3. The attempt at a solution So I've tried finding the distance according to the angle...but I'm confused. Why is the index of refraction included? I got 1.0457*10^-4 as the angle. Then divided that by half, 5.229*10^-5, call it [tex]\theta[/tex]2. found that the distance from the eye to the car would be 60tan[tex]\theta[/tex]2=6.574*10^7 cm. The question also said that the answer you would get would be more than what the eye can resolve, but I still think this might be off. Maybe it has to do with the lens being diffraction limited?