Is this process known as "total internal reflection"? Or is it called something else? What is the name of this process that causes the entire material to light up even though the light is applied only to one side? Take a look at the photos so you can see what I am asking about. Notice how the light in the key chain is only applied from one direction, yet the entire keychain appears to "light up". Is that caused by total internal reflection? I cannot post full links right now so find the picture on tinyurl: tinyurl dot com/cu989ek You also see it on some exit signs like this: tinyurl dot com/dxl2jd2 A few other examples: tinyurl dot com/c58oqsv tinyurl dot com/cor6t22 Wikipedia defines total internal reflection as:"Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface." But that does not seem to be what is happening in the photos I showed you above. From the photos above, the "critical angle with respect to the normal to the surface" does not seem to matter. Or am I missing something here?