Practice question

**Spherical refracting surface** power P = (n₂-n₁)/R, lens power sum of two surfaces. Lens maker derivation combines two refractions, sign of R₂ negative for second surface convex opposite direction, yielding 1/f positive for convex lens. A concave lens diverges light rays, making them appear to originate from a point on the same side as the object when traced backward. This results in a virtual image that cannot be projected on a screen, always forming on the object’s side regardless of its position. Substituting values gives Because rays diverge and appear to come from the same side, which matches expected image position and magnification from mirror/lens