Thin Lens Equation
Interactive simulation — adjust parameters and watch the visualization update in real time.
Live graphs
How it works
The Gaussian thin-lens formula relates object distance, image distance, and focal length. The graph of d_i versus d_o is a hyperbola with a vertical asymptote at d_o = f for a converging lens. Moving the pink point with the d_o slider shows how small changes near the focal plane send the image to infinity or flip the sign of d_i.
Key equations
1/f = 1/d_o + 1/d_i
d_i = d_o f / (d_o − f) · m = −d_i/d_o