Practice question

**Refraction through prism** deviation δ = i+e-A, minimum when i=e, symmetrical path, r₁=r₂=A/2, n = sin[(A+δ_m)/2]/sin(A/2). In water n_rel = n_prism/n_water =1.5/1.33=1.128, so δ_m reduces because relative index lower, new δ_m from formula with n_rel. Shift = t ( 1 - (1/n) ) . t = 8.1 cm , n = 1.62 . Shift = 8.1 ( 1 - (1/1.62) ) = 8.1 ( 1 - 0.617 ) = 8.1 × 0.383 ≈ 3.1 cm . Substituting values gives 3.1 cm, which matches expected image position and magnification from mirror/lens formula 1/f = 1/v - 1/u (lens) or 1/f = 1/v + 1/u (mirror), confirming sign conventions and refraction principles.