|
The critical angle for a water (n=1.33) - zircon (n=1.92) boundary is 44 degrees. Which of the following diagrams depict incident rays which would undergo total internal reflection (TIR) at the angle shown? List all that apply ... .
(Note: The boundary may be between glass (n=1.53) and diamond (n=2.42).)
|
|
Requirements for Total Internal Reflection (TIR):
Two requirements must be met for total internal reflection to occur. First, light must be in the more dense medium heading toward the boundary with the least dense medium. Second, light must be approaching the boundary with an angle of incidence that is greater than the value of the so-called critical angle.
|
|
Two requirements must be met for TIR to occur (see Know the Law section above). Each diagram shows two media (labeled and shaded), the boundary which separates them (solid black line) and the incident ray (red line with arrowhead). For total internal reflection to take place, the incident ray must be in the more dense medium (refer to Know the Law section below) at an angle of incidence that is greater than the critical angle. If uncertain, measure the angle of incidence (between the incident ray and the normal line) to insure that it is greater than the stated critical angle.
|
|
|
Optical Density and the Index of Refraction:
Every material is identified by a unique index of refraction value. The index of refraction value is an experimentally determined value which provides a relative measure of the optical density of that material. The higher the index of refraction value, the more optically dense a material is.
|