What is the effect of using high-beam headlights in fog?

Using high-beam headlights in fog is not effective because the light emitted can reflect off the water droplets in the fog, creating a blinding effect that reduces visibility. In such conditions, the light scatters, causing a veil of brightness that obscures the view ahead rather than enhancing it.

This phenomenon happens because fog consists of tiny water droplets suspended in the air, and high beams produce intense illumination that is often too intense for such conditions. As a result, when the bright light hits the fog, it reflects back towards the driver, leading to a whiteout effect that severely hampers visibility.

Therefore, in foggy conditions, drivers are advised to use low-beam headlights, as they provide sufficient illumination of the road without reflecting back into the driver's eyes, allowing for better visibility and safer driving.