What happens if you microwave nothing?

Chef's answer
What happens if you start the microwave oven with nothing inside? The magnetron creates microwaves that travel into the cooking chamber and should be absorbed there. If there is no food (or rather no water-containing food), those microwaves will not be absorbed and will eventually find their way back to the magnetron.20 Mar 1995
Frequently asked Questions 🎓
Microwave do not explode. Sometimes, the heat generated in a object by microwaves causes the object or something sealed within it to heat and explode.
Cooking raw meat in the microwave is safe but the food must reach proper temperatures. Raw beef, pork, and lamb should reach 145 degrees Fahrenheit, ground meats should reach 160 F and all poultry should reach 165 F. ... If food is thawed in the microwave, it must be cooked immediately.1 Nov 2017
Overheated food or packaging is the main culprit According to Bob Schiffmann, a 50-year veteran of the microwave industry and president of the International Microwave Power Institute,1 microwave fires usually start for the same reason that oven or stovetop or grill fires do: "It's simply due to [the food] overheating."20 May 2020
One fire is too many, but the numbers suggest that microwaves are quite safe. Estimates can vary, but at least 90 percent of US households have a microwave. According to the National Fire Protection Association, microwaves cause 4 percent of cooking-related house fires per year (PDF) and 1 percent of associated deaths.20 May 2020
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