Key Points — Ultra-Concise Revision Bullets — Summary

Mirror: 1/v + 1/u = 1/f; m = **−**v/u; concave f < 0; convex f > 0; u always negative.
Lens: 1/v − 1/u = 1/f; m = v/u (no minus); convex f > 0; concave f < 0.
TIR: denser → rarer medium AND angle > θ_c = arcsin(n_{2}/n_{1}). Both required. Diamond: θ_c = 24.4°.
Prism: δ = (i+e) − A; minimum: i = e, n = sin((A+δ_m)/2)/sin(A/2); thin prism only: δ = (n−1)A.
Instruments: Microscope objective has SHORT f; Telescope objective has LONG f; P = $P_{1}$ + $P_{2}$ ; M_telescope = −f_o/f_e; L = f_o + f_e.