An interaction of light and matter will result in an optical phenomenon. There are different forms of optical phenomena, an example of it are scattering, diffraction, interference, reflection and transmission of light.
Diffraction:
Diffraction is defined as the change in the directions and intensities of a group of waves after passing by an obstacle or through an aperture whose size is approximately the same as the wavelength of the waves. The bending and spreading of light on small obstacles are some characteristics of diffraction. Images shown below are examples of diffraction of light-matter interactions.
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| Figure 1: Example of Diffraction (Light entering and leaving a glass prism) [1]. |
Interference:
The superposition of two or more wave that produces a new pattern is called interference. Interference occurs in two forms, constructive and destructive interference. Constructive interference is when the superimposed waves are in phase resulting to a summation of amplitude. Meaning, the troughs and peaks of the waves are lined up. On the other hand, destructive interference is when the troughs and peaks of the waves are out of phase which means the sum of their amplitude goes to zero.
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| Figure 2: Example of Interference (Hologram) [2]. |
Reflection:
A light scattered in the opposite direction of incident light is defined as reflected light. The law of reflection states that the angle of the incident ray is equal to the angle of the reflected ray with respect to the normal of the medium. Shown below is representation of the law of reflection.
Reflections of light can either be specular (glossy), body (matte) or inter-reflection depending on the nature of the interface. Below are the examples of reflections.
Specular reflections are almost the same as a light reflected on mirrors.
Body (matte) means that the object will not be directly visible in the scene; instead, the background color will be shown in its place. However, the object will appear normally in reflections/refractions and will generate indirect illumination based on its actual material
Inter-reflection is the phenomenon the occurs when a reflection of others objects are seen in the object of interest.
Transmission:
Transmission is the act of passing something on in another place. Transmission is the property of a substance to permit the passage of light, with some or none of the incident light being absorbed in the process.
Images Exhibiting Specific Light-Matter Interaction Phenomena
Body (Matte):
Diffraction:
Transmission:
Interreflectivity:
Sources:
[1] http://electron9.phys.utk.edu/phys136d/modules/m10/geometrical.htm
[2] Credits to Dr. Percival Almoro and the Photonics Laboratory for the imaging.
[3] Mulan - Reflection - http://www.youtube.com/watch?v=5A_Rl8aQxII
[4] http://en.wikipedia.org/wiki/Specular_reflection
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