Prism Angle Relationship — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Prism Angle Relationship Applies to refraction of a light ray through a triangular glass prism in Ray Optics. Draw normals at the point of incidence and point of emergence. Use the property that the sum of angles in the quadrilateral formed by normals and prism apex is 360 degrees. Use the property that the exterior angle (deviation) of the triangle formed by the ray intersection is the sum of interior opposite angles. Combine geometrical relations to find A + Δ = i + e. The prism material must be transparent. Valid only when the ray emerges from the second refracting face (no Total Internal Reflection preventing emergence). Angles must be in the same unit (degrees or radians). Believing that angle of incidence (i) is always equal to angle of emergence (e) (this is only true at minimum deviation). Confusing the prism angle (A) with the critical angle. Thinking the relation depends on the refractive index directly (refractive index determines values of i and e, but the geometric sum relation holds regardless).