Final answer:
While the original question about the safe following distance when using low beam lights is not directly answered, the discussion is centered on the human eye's ability to resolve car headlights at a distance using the diffraction limit, which is part of Rayleigh's criterion in physics.
Step-by-step explanation:
The question pertaining to the recommended distance between vehicles when using low beam lights seems to be conflated with a series of questions about the resolving power of the human eye based on diffraction limits. Unfortunately, the provided choices (a) 50 feet (b) 100 feet (c) 150 feet (d) 200 feet do not directly apply to the diffraction-based questions about resolving car headlights at a distance. However, general driving recommendations suggest maintaining a considerable gap between vehicles for safety, which varies depending on speed and conditions, but is not typically specified in feet relative to low beam light usage.
Regarding the human eye's ability to resolve car headlights, the pupil diameter plays a crucial role in determining the limit of resolution due to diffraction effects. We use the Rayleigh criterion and assume an average wavelength of light to calculate the angle between two just-resolvable points, which can then be applied to find the maximum distance at which car headlights, typically 1.3 meters apart, can be resolved. The result of this calculation would be relevant to establish when it's safe to cross a road in the presence of an oncoming car, as mentioned in part (g) of the question. Yet, this is more a matter of visual perception rather than a prescribed safe distance when using low beams for vehicle separation during night driving.