For example why are some surfaces/materials shiny, like some metals, fabrics, plastics etc. but not others.
[Edit: Thanks, two good answers that explain it well]
In: 2
Depends on how smooth the surface is. If it’s rough on a microscopic scale it will look matte to us.
This has to do with light reflections – a smooth surface will reflect all the light into the same direction and a rough surface will scatter it randomly.
Reflection of light. Specifically, reflection of light in such a way that light from a given point will reflect into your eye mostly from a small region on the surface, making that region very bright compared to the surrounding, and as you move your eye the region change.
It’s determined by 2 important factors.
– Roughness of the surface: if the surface is not smooth and flat enough, light will be too scattered that the light that do get reflected into your light will come from only a small amount of random positions, instead of consistently from a small region.
– Material’s ability to reflect light: a significant part of light get reflected. Not necessary near 100% (otherwise it would look like a mirror), but large enough. At the atomic level, electrons must be free enough that it response to the light wave in such a way that they produces addition wave that looks like the reflection of the original wave.
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