Additional Math Pages & Resources

Friday, June 24, 2011

It's not clear to me, Part V

Friday's here already and I'm still working on the subject of things you can see through, but not clearly.

Two days ago we were able to compare how color changes the way light comes through an ashtray, or vase, or drinking glass. Although we didn't get deeply into the physics of this, it seems light is composed of rays of various wavelengths, and when it passes through colored glass, some rays are blocked, and some colors don't come through. [Click here to see the colors again]. In general though, the glass remains transparent (see-through).

Today we look at texture and how it affects glass. Here's another 9-image grid - each picture was taken through a different piece of textured glass [click on the image to enlarge it].


These textures were created to give windows an interesting appearance, and to enhance privacy. A textured glass like #4 is normally used in a bathroom to prevent people from seeing in. Examples #7 and #8 wouldn't be as good for privacy, but they do distort the view a bit.

Taking a step back with the camera, you can see how the textured parts of this glass obscure the houses and things in the distance, while still letting in plenty of light and giving your eye something to look at in the foreground. These are the same pieces of glass I photographed in samples #1, #2 and #3. What can we call this effect?


  1. Opacity means a substance is completely impenetrable to (absorbs) visible light
  2. Transparency is light passing through a material without diffusion (you can see clearly through it)
  3. Translucency is when light comes through a substance but is diffused (you cannot see clearly through it)
  4. Absorption means a material allows some wave lengths through and not others; this results in colors
  5. Refraction is light being redirected or bent as it passes through the glass
  6. Reflection is light being bounced back rather than passing through glass

Glass with surface textures or internal elements tends to refract and reflect the light. The glass become translucent rather than transparent. For a more detailed discussion, check this Wikipedia article.

What does this have to do with math (you might ask)? Plenty. In geometry, you learn about rays, angles, parallel, perpendicular, reflection, etc. Without this knowledge, there can be no clarity about glass.


Colored art glass displayed underwater, in an aquarium where light is passing through both water and glass (that is a baby Moray eel peeking out at us).