Final answer:
In foggy conditions at night, it's best to use low beam headlights and fog lights to prevent light scattering and reflection, which impair visibility.
Step-by-step explanation:
When driving through fog at night, it is best to use your low beam headlights and fog lights, if you have them. Driving with high beam lights in fog is like shining your lights on a mirror. The high beams cause light to scatter in the water droplets that make up the fog, which can reflect the light back at you and further impair visibility.
This effect can be understood by considering the principle of reflection observed when light interacts with reflective surfaces such as mirrors. Most modern cars are equipped with headlights that use parabolic mirrors to create a directional beam. The use of low beams directs the light downward, reducing the amount of light that gets reflected back by the fog.