Prism Refractive Index Formula — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Prism Refractive Index Formula Applicable to optical prisms where the condition of minimum deviation is met. Use the prism formula A = r1 + r2 and D = i + e - A At minimum deviation, i = e and r1 = r2 = A/2 Substitute values to get i = (A + Dm)/2 Apply Snell's Law at the first surface: n = sin(i) / sin(r1) Substitute i and r1 into Snell's Law The ray must undergo minimum deviation where angle of incidence equals angle of emergence Prism must be placed in a rarer medium (usually air) Applies to monochromatic light Assuming this formula applies to any arbitrary angle of deviation Using the formula for thin prisms (where A < 10 degrees) without the small angle approximation Forgetting that 'n' is the relative refractive index if the prism is not in a vacuum or air