Go against the moon: the brighter the puddle; The darker the soil is.
Walk with your back to the moon: the darker the puddle; The brighter the soil.
Because moonlight is specular reflection on water and diffuse reflection on soil.
The reflection of light is an optical phenomenon. Refers to the phenomenon that when light propagates to different substances, it changes the direction of propagation at the interface and returns to the original substance. When light meets the surface of water, glass and many other objects, it will be reflected. When light changes its propagation direction at the interface between two substances and returns to the original substance, it is called light reflection.
The reflected light is on the same plane as the incident light and the normal line; Reflected light and incident light are separated on both sides of the normal; The reflection angle is equal to the incident angle. It can be summarized as: "Three lines * * * plane, two lines are separated, and the two angles are equal." Light is reversible. In the phenomenon of light reflection, the light path is reversible.