No, it is not safe to open the door of a microwave when it is still actively microwaving. Microwaves are designed with safety mechanisms to prevent radiation leakage, and one of these safety features is an interlock switch that automatically turns off the microwave's magnetron (the component that generates the microwaves) when the door is opened.
However, there can be instances where the interlock switch malfunctions or is damaged, which could potentially result in the magnetron continuing to emit microwaves even with the door open. Microwaves are a form of electromagnetic radiation, and exposure to high levels of microwave radiation can be harmful to your health.
Exposure to microwaves can cause tissue and thermal burns, eye injuries, and other adverse health effects. Additionally, opening the door while the microwave is in operation can result in hot steam or food splattering, posing a risk of burns or scalds.
To ensure your safety, it's important to always follow the manufacturer's instructions and guidelines for operating a microwave. This includes waiting for the cooking cycle to complete and the microwave to turn off before opening the door. If you suspect that your microwave's safety mechanisms are not functioning properly, it is advisable to have it inspected and repaired by a qualified professional.