Excuse me, why is this?

Classification: Life >> Common sense of life

Problem description:

On a rainy night, what is the phenomenon of walking behind the headlights to observe the rainy road?

The answer is: when walking against the light, "white is water, underwater may be a deep pit, and darkness is land. Walking against the light is just the opposite."

Excuse me, why is this?

Analysis:

Hehe, first of all, we should understand two concepts, specular reflection and diffuse reflection.

Specular reflection:

As the name implies, it is a reflection phenomenon that occurs on a surface as smooth as a mirror. Under the irradiation of parallel light, all the rays are reflected in the same direction.

Diffuse reflection:

The reflection phenomenon of rough surface reflects light in different directions under the irradiation of parallel light. Most of the reflection phenomena we come into contact with are diffuse reflection from rough surfaces.

Now let's look at your question. When the light hits the water, it is specular reflection, so you can only see the reflected light in a certain direction. If you make a light path diagram yourself, you will find that this direction is the direction facing the light.

When light shines on the road, this rough surface will reflect light in all directions, and we can see as much light as possible in any direction.

When facing the light, we see the light reflected from the water surface and feel white. Of course, the road surface also reflects light, but compared with the strong reflection of the water surface, it is of course dwarfed. We thought it was dark there.

When your back is to the light, the water will not reflect light in this direction. Relatively speaking, although there is not much light reflected from the road surface, our eyes will still feel that the water is black and the road is brighter.

Of course, the road surface brightness when facing away from the light is much darker than the water surface brightness observed when facing away from the light. The so-called "just the opposite" is not exactly the opposite, but a general statement, which is not very accurate.

Also, the light emitted by street lamps cannot be regarded as parallel light. Street lamps are point light sources, so you can see the light reflected from the water in a large range. However, the range of parallel light after reflection is much smaller. You can make your own light path diagram to prove this point.

It has been a long time since graduation. I don't remember the definitions of specular reflection and diffuse reflection very accurately. I also need to refer to physics books. It's in the textbook of senior two, hehe.