Light paths
Move parallel beams through seven refraction and reflection experiments.
1–10 lasers stay parallel and move together. Use the sliders or arrow keys for fine adjustments.
Convex lens
Move the parallel beams up and down to see them bend toward the optical axis.
Concave lens
Send light through a lens that is thin at the center and thick at the edges.
Convex + concave lenses
Follow each bend through a convex lens and then a concave lens.
Parallel-sided glass
Swing the lasers around the glass center and compare incoming and outgoing directions.
Convex mirror
Watch parallel light reflect from an outward-curving mirror.
Concave mirror
Aim a parallel beam at an inward-curving mirror.
Diffuse reflection
Let parallel beams meet tiny surfaces with different orientations.
How it works +
In the first three experiments, lasers point horizontally right and move vertically together. In the last four, the bank rotates around the optical element’s center. Lasers stay parallel and the count applies to all experiments.
Refraction is calculated at each actual surface, using refractive indices of 1 for air and 1.5 for glass. Lenses and curved mirrors have spherical surfaces. Near-axis rays converge near a focus or appear to diverge from a virtual focus; edge rays exhibit spherical aberration.
Dashed backward extensions indicate a virtual focus, not actual light. For parallel-sided glass, dashed guides show the original incoming direction to reveal lateral shift. Enable normals to see the surface orientation at each interaction.
Diffuse reflection uses a fixed rough surface and local normals. Rays that miss the finite elements continue straight. This is a two-dimensional geometrical optics model without diffraction, interference or intensity splitting at partially reflecting surfaces.
References:OpenStax · Snell · OpenStax · Mirrors