Optics you can teach by touching.

Static lens ray diagrams show one configuration. OpticSketcher shows all of them: drag the object closer to the focal point and watch the image flip from real to virtual, rotate a prism and watch white light spread into a spectrum, turn a polarizer and watch the transmitted intensity follow Malus's law. Because rays are traced by real physics, not drawn by hand, the demonstration is always correct, for any question a student asks.

It runs in the browser on any device, so a demonstration built for the lecture screen works identically on every student's laptop, tablet, or phone. Share a sketch with one link and the whole class opens the same setup.

Optics clicks when you can see cause and effect. Instead of memorizing which side of the lens the image forms on, place a source and a lens and find out - then move things until you understand why. Immediate visual feedback turns formulas into intuition: Snell's law becomes a bending ray you can steer, and polarization becomes a state you can filter, rotate, and measure with a sensor.