Total Internal Reflection
TIR, though a relatively easily-explained optical phenomenon, has many interesting and useful applications. Occuring when the incident light strikes the boundary between mediums at a critical angle, total internal reflection has uses in optical fibers, spacial filtering, and touch screen technology.
In the last few years, progress has been made in the field of multi-touch systems, using frustrated total internal reflection. With their ability to pick up signals from multiple users and touch points, multi-touch systems represent exciting possible strides forward in both efficiency and convenience.
1, and 2 - some multi-touch links .
Among many high schoolers, the term "polarized light" brings to mind only linearly polarized light. However, linear polarization is not the only way light can be polarized. Linear polariztion, it turns out, is just a special case of elliptical polarization. Other forms of polarization include circular, radially, and azimuthally polarized light.
In the animal kingdom, many species, especially insects, are able to see polarized light and use it to aid their navigation. For most of these animals, linearly polarized light is the view that they see. However, one species, the lovely mantis shrimp, can see circularly polarized light as well.
An interesting article regarding the difficulties of animals' polarized-guided navigation on cloudy days
Adaptive Optics, pt. 2?
Remember Anand's lecture on the use of adaptive optics in seeing into space? Well, here's another use, one much closer to home.
Pretty sweet article relating biology to many different aspects of optics