A photon can interact with a surface in a number of ways:
- Absorption: the energy from the photon is transformed into the internal energy of the absorber (e.g., thermal energy).
- Reflection: the energy from the photon changes direction back into the medium form which the photon originated.
- Diffuse Reflection: an incident ray of light is reflected in many directions, not just one angle.
- Specular Reflection: an incident ray of light is reflected in one direction (e.g., in mirrors).
- Transparency: an incident ray of light travels through an interrupting medium unchanged
- Refraction: an incident ray of light travels through an interrupting medium, but alters direction
- Fluorescence: an incident ray is absorbed and emitted, often at a different wavelength
- Subsurface scattering: an incident ray goes into a surface, bounces around one or more times, and comes back out at a different places than the point of entry
- Phosphorescence: an incident ray is aborbed and emitted at some later time
- Interreflection: an incident ray strikes reflects some energy, which strikes and illuminates nearby surfaces
Bidirectional reflectance distribution function (BRDF)
The physics of color
The eye and color perception