Drag the object · rays redraw live

🔍 Lens & Mirror

Drag the arrow along the optical axis and watch three principal rays find the image live: converging or diverging lens, concave or convex mirror. Real images draw solid, virtual ones dashed, and the caption tells you which device you just built — camera, projector, magnifier or car mirror.

Object d 30 cm Focal |f| 12 cm Height h 6 cm

Image distance d′

Magnification m

Image height h′

Formulasign convention: real +

Three principal rays: ① parallel to the axis → refracts through F′ (or appears to come from it), ② through the optical center — straight, ③ through F → leaves parallel. Where they (or their dashed extensions) meet is the image. Thin-lens/mirror equation 1/f = 1/d + 1/d′, magnification m = −d′/d.