At a surface between two media with different refractive indices, incident waves are reflected back, and the refractive index of the medium is altered (e.g., light refraction changes).
The following types of reflection are distinguished:
- Directed Reflection: On smooth, polished surfaces, light is predominantly reflected in a directed manner, where the angle of reflection (reflection angle) is equal to the angle of incidence.
- Diffuse Reflection: On rough surfaces or opaque materials with internal scattering centers (e.g., frosted glass), the incident light is diffusely scattered. (Example: Ulbricht sphere)
- Total Reflection: Light is completely reflected at the surface. This occurs only with ideally transparent samples.
Absolute Reflection: In this case, the percentage of absorption and transmission is zero.