Reflection And Refraction

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.

The current is related to the drift velocity by the equation: where:
- is the current,
- is the electron density,
- is the charge of an electron ( ),
- is the cross-sectional area of the conductor, - is the drift velocity.
Step 1: Rearrange the equation to solve for .
We can rearrange the equation to solve for :
Step 2: Substitute the given values.
Substitute the given values into the equation:
Step 3: Calculate the drift velocity.
Now, calculate the value of :
Step 4: Conclusion.
The drift velocity is: