Why are the street lamps dim on rainy days?

There are several reasons why street lamps are dim in rainy days:

First of all, rainy weather will lead to the increase of water vapor in the air, which will make light scatter in the process of propagation. The scattering of light in water vapor will change the direction of light propagation, thus making the lighting range of street lamps blurred and uneven. Therefore, the lighting effect of street lamps in rainy days will be relatively poor.

Secondly, the rain in rainy days will attach to the lampshade of street lamps, forming a water film. This water film will block the transmission of light and reduce the illumination brightness of street lamps. At the same time, the water film will also reflect the light, thus narrowing the lighting range of street lamps. So street lamps will look dim in rainy days.

In addition, raindrops in rainy days will continue to fall on the lampshade of street lamps, forming water droplets. These water droplets will scatter light and change the direction of light propagation, thus making the lighting range of street lamps vague and uneven. At the same time, water droplets will also absorb and reflect light, reducing the lighting brightness of street lamps. So street lamps will look dim in rainy days.

Finally, the rain in rainy days will make the road slippery, thus increasing the reflected light of street lamps. These reflected rays will make the lighting range of street lamps blurred and uneven. At the same time, the slippery road surface will also reflect the light of other light sources, reducing the lighting brightness of street lamps. So street lamps will look dim in rainy days.

To sum up, the dark street lamps in rainy weather are mainly caused by the light scattering caused by the increase of water vapor in the air, the water film and water droplets formed by the rain blocking the scattered light, and the reflection of light by the slippery road surface. These factors make the lighting effect of street lamps worse, resulting in darker street lamps.