Final answer:
To signal an approaching vehicle to dim their headlights at night, flash your headlights briefly. If they don't respond, look toward the right edge of the road. The dimming of lights occurs due to changes in electrical resistance or voltage, such as with a draining car battery.
Step-by-step explanation:
To signal an approaching vehicle to dim their headlights at night, you should flash your headlights briefly. This is a universal signal that drivers use to communicate with each other when driving in low-light conditions. Once the approaching vehicle sees your flash, they should understand that their headlights are too bright and should be dimmed to avoid impairing your vision while driving.
If the oncoming vehicle does not dim their lights after you signal them, you should avoid looking directly at the light to protect your eyes from being overwhelmed by the brightness. Instead, it's safer to direct your gaze slightly to the right edge of the road to ensure that you maintain visibility without being blinded.
This is similar to other occurrences where lights may dim, such as when refrigerator lights briefly dim when the motor starts. In your car, when you start the engine, the lights may also dim slightly. This dimming effect is usually related to changes in electrical resistance or voltage, like when a car battery's output voltage decreases as the battery drains, leading to the gradual dimming of the headlights when the battery runs out of energy.