Suppose you shine a beam of light on a glass surface. Some of it will get reflected back. Some of it will be absorbed by the glass and some will continue to pass into the glass after bending by some angle (refraction). However, when light tries to do the opposite, i.e. go from glass to air if its angle of incidence is larger than some value called 'critical angle of incidence', whole of it gets reflected back inside the glass. None of it comes out in the air. This is called total internal reflection. It happens only when both these conditions are satisfied:
1)Light is trying to go from a denser medium to a rarer medium (e.g. glass to air).
2) Its angle of incidence is larger than a certain critical angle.
Now, you see, I am a thick skulled being (figuratively).
A thick skull is obviously a denser medium. So when some thought of self-enLIGHTenment tries to come out of my mind, it has to cross the thick skull, coming from my brain. Thus it has to go from rarer (very few neurons in the whole big cranium) to denser medium (thick skull). This is opposite of the required condition 1). Since comdition is not met,
Total Internal Reflection
never occurs ;). I can't violate natural laws of physics can I?
P.S: What do you call a geeky reptile?
A : A gecko?