Final answer:
Use low beams when following within 200-300 feet of another vehicle to avoid glare. Visibility decreases with distance just like a camera flash loses effectiveness when the subject is too far.
Step-by-step explanation:
You should use your low beams when following a car to ensure that you are not blinding the driver ahead with your high beams. While specifics can vary by jurisdiction, a common rule of thumb is that you should switch to low beams when you are within 200-300 feet of the vehicle ahead to prevent glare. The visibility of car headlights is significant because it affects both how well you can see and how well you are seen by others on the road. When the subject, such as another vehicle, is far away, the effectiveness of your lights in illuminating that vehicle diminishes, similar to how a camera flash is ineffective at lighting subjects that are too far away.