1557. Could a magnetron be tuned to heat air, oxygen, or nitrogen? Is it a specific frequency or a range? What is the frequency? — VM, Martinsville, Indiana
No, those gases don't absorb microwaves significantly regardless of frequency. Diatomic molecules are nearly oblivious to long wavelength electromagnetic waves. In fact, that's why they don't contribute to the "greenhouse effect." Oxygen does have an unusual absorption band in the near infrared, but that's about it.