No, it is not safe to use a microwave oven with the door opened, even if there is no food inside. Microwaves emit electromagnetic radiation, including microwave radiation, which is absorbed by water, fats, and sugars in food, causing them to heat up.
When you operate a microwave oven with the door open, the microwaves can escape and pose a potential risk. These microwaves can be harmful to your body, particularly to your eyes and other sensitive tissues.
Microwave ovens are designed with safety mechanisms that prevent them from operating when the door is open. These mechanisms include interlock switches that cut off power to the magnetron (the component that produces microwaves) when the door is opened. This is done to protect users from exposure to the microwaves.
To ensure your safety, always keep the microwave oven door closed and only operate it when there is food or a microwave-safe container inside. If you suspect that your microwave oven is not functioning properly or the safety mechanisms are not working as they should, it is advisable to have it inspected and repaired by a qualified professional.