反射是什么?

Reflection is when light bounces off an object. If the surface is smooth and shiny, like glass, water or polished metal, the light will reflect at the same angle as it hit the surface. This is called specular reflection.

Reflection occurs when a light ray deviates from its straight line path when it hits a surface. Reflections in general can either be hard or soft. A hard reflection is characterized by a phase shift of pi and occurs when a light ray reflects from a surface with a higher refractive index that the original medium. A soft reflection does not involve a phase shift and occurs when a light ray reflects from a surface with a lower refractive index that the original medium. These are consequences of solutions of the wave equation.