(a) Deduce the expression, by drawing a suitable ray diagram, for the refractive index of a triangular glass prisms in terms of the angle of minimum deviation (D) and the angle of prism (A).
Draw a plot showing the variation of the angle of deviation with the angle of incidence.
(b) Calculate the value of the angle of incidence when a ray of light incident on one face of an equilateral glass prism produces the emergent ray, which just grazes along the adjacent face. Refractive index of prism is `sqrt2`

Explanation

### Step-by-Step Solution

#### Part (a): Deduction of the Expression for Refractive Index

1. **Draw the Ray Diagram**:
- Draw a triangular glass prism labeled ABC.
- Draw an incident ray OP striking face AB at point P, making an angle of incidence \( I_1 \).
- Draw the refracted ray PQ inside the prism making an angle \( R_1 \) with the normal at point P.
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