Final answer:
The question deals with the angular resolution of the eye in the context of distinguishing car headlights. The theoretical limit lies at several kilometers, but for safe driving, visibility should be much clear and multiple factors should be considered.
Step-by-step explanation:
The question relates to the resolution of the human eye and the ability to distinguish two separate points, such as the headlights of a car. The ability to resolve two points is determined by the angular resolution of the eye, which can be estimated using the Rayleigh criterion.
According to this criterion, an average human eye with a pupil diameter of around 0.40 cm can resolve points that are approximately 1.22 times the wavelength of light divided by the diameter of the pupil.
With headlights 1.3 m apart, assuming ideal conditions and using visible light with a wavelength of about 550 nm, this results in a maximum resolution distance of several kilometers.
However, for safe driving practices, one should ensure clear visibility well beyond this theoretical resolution limit, taking into account variables such as speed, weather conditions, and reaction time. In practical terms, always make sure there is enough clear space to pass safely, which typically means visibility for at least a few hundred meters in normal conditions.