Refraction and Lenses - Mission RL6 Detailed Help

Total internal reflection (TIR) does not always occur when light moving through one medium strikes a boundary with another medium. Two requirements must be met for TIR to occur. Which two statements below express these two requirements? Light must be _____.


 
Definition of Total Internal Reflection:
Total internal reflection (TIR) is the phenomenon that occurs when all the light which is approaching a boundary with a transparent medium undergoes reflection and remains within the original medium.


 
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.


 
Many beginning students of physics become quite confused by the concept of a critical angle and its relationship to total internal reflection. It is a commonly held wrong belief that TIR occurs when the incident angle is equal to or even less than the critical angle. But don't be fooled! The incident angle must be greater than the critical angle for total internal reflection to occur.