Question

The phenomenon of total internal reflection occurs when a ray of light travels from

• A. rarer to denser medium
• B. denser to rarer medium
• C. air to water
• D. vacuum to air
• E. water to glass

Hint:

Think of the boundary like a barrier. Light can only "bounce back" if it's trying to escape a crowded (denser) room into an empty (rarer) hallway at a very shallow angle. If it's going into the "crowded room," it just enters and gets slowed down.

Answer 1

The Correct Option is B

Concept:
Physics - Ray Optics (Total Internal Reflection).
Step 1: Understand the conditions for TIR.
Total Internal Reflection (TIR) is the complete reflection of a light ray back into its original medium. For this to happen, two specific conditions must be met:

• The light must travel from an optically denser medium to an optically rarer medium.
• The angle of incidence in the denser medium must be greater than the critical angle for that pair of media.

Step 2: Analyze the direction of bending.
When light goes from denser to rarer, it bends away from the normal. As the angle of incidence increases, the refracted ray bends further away until it grazes the surface (critical angle) and eventually reflects back into the denser medium.
Step 3: Evaluate the options.

• (A), (C), (D), (E): These all describe light moving into a denser medium (where it bends \textit{toward} the normal), making TIR impossible.
• (B): Correctly identifies the denser to rarer transition.