What is Total Internal Reflection (TIR) and its applications?

Total Internal Reflection (TIR):

• Definition: Complete reflection of a ray of light back into the denser medium when angle of incidence exceeds critical angle at boundary with rarer medium.
• Necessary Conditions: Light must travel from denser to rarer medium, and angle of incidence > critical angle.
• Applications: Optical fiber communications, mirage in deserts, sparkling of diamonds, and endoscopes.