Practice question

**Spherical mirror reflection** follows law θ_i = θ_r, focal length f = R/2, concave R negative, convex positive. Object beyond center C (u > 2f) forms image between F and C diminished, at C same size, between C and F magnified, beyond F forms at infinity, illustrating mirror equation. Focal length: f = -12 cm (concave mirror). Object distance: u = -18 cm . Mirror equation: (1/v) + (1/u) = (1/f) . (1/v) + (1/-18) = (1/-12) ⇒ (1/v) = (1/-12) + (1/18) = (-3 + 2/36) = (-1/36) . v = -36 cm (real image). Substituting values gives 36 cm, which matches expected image