Spherical mirrors: image formation and mirror formula
Reflection and refraction · Physics
Convex lens ray diagram
Interactive 3DMove the object and watch parallel rays converge at the focal point while the image obeys 1/f = 1/v + 1/u.
Controls
Drag the sliders or type a value — the simulation updates live.
cm
3cm10cm
Study notes
Example: Find the image distance (di) and magnification (m) for a concave mirror with focal length f = 20 cm when the object is placed at do = 30 cm. Step 1: Write the mirror formula: 1/f = 1/do + 1/di. Step 2: Plug in the known values: 1/20 = 1/30 + 1/di. Step 3: Find 1/di: 1/di = 1/20 - 1/30 = (3-2)/60 = 1/60. Step 4: Solve for di: di = 60 cm. Step 5: Compute magnification: m = -di/do = -60/30 = -2. Result: The image is 60 cm in front of the mirror (real) and is twice as tall as the object, but upside down (negative magnification).