Microwave ovens heat food effectively because microwaves operate at 2.45 GHz, which causes polar molecules, primarily water, to oscillate rapidly through dielectric heating. This process generates heat by making molecules bump into each other, unlike visible light, which heats only surfaces due to its limited penetration depth. While light can also generate heat, it does not penetrate food deeply, making it less effective for cooking. The choice of 2.45 GHz was largely due to it being an unused frequency at the time of microwave oven development, not because of any unique heating properties. Understanding these principles clarifies why microwaves are preferred for heating food over visible light.