Visible photon has more energy than a microwave photon. A microwave oven pumps out 1,000 watts of energy or more by generating a whole bunch of photons. Your conventional oven actually puts out even more energy (3,000 watts for an electric, 5,000 for gas). Most of that is infrared, which has less energy than visible light but more than a microwave.Thus the answer is shorter than visible light.