The microwave oven operates at around the same frequency as wifi (2.4GHz). This is far less energy than even infrared, let alone visible light. These waves are flying all over the place anywhere you go and they’re totally harmless.

The microwave oven is a lot more powerful than a wifi transceiver but all that power is contained inside the interior which is designed as a faraday cage to block and reflect the waves back toward the food. The amount of microwave energy that actually escapes the oven is minuscule to the point where it just barely interferes with nearby wifi signals.