No, microwaves are not harmful to humans when they are not being used. When a microwave is not in use and the door is properly closed, the microwaves are contained within the microwave oven and pose no risk to people in the vicinity.
Microwaves are a form of electromagnetic radiation, just like visible light, radio waves, and infrared radiation. When you turn on the microwave to heat food, it produces microwaves that excite the water molecules in the food, generating heat and cooking the food. However, these microwaves are confined inside the microwave oven and do not escape as long as the oven is functioning correctly and the door is undamaged and closed.
Modern microwave ovens are designed with safety features, including an interlock mechanism that automatically shuts off the microwave's power when the door is opened. This prevents microwaves from being emitted while the door is ajar.
It's essential to use microwave ovens properly, following the manufacturer's instructions and not tampering with the device or its safety mechanisms. As long as the microwave is in good working condition, there is no need to worry about harmful exposure to microwaves when the oven is not in use.