Microwave oven runs with door open

Question

The microwave runs with the door open. Goes off as usual when the door is closed, but when door is opened the light goes on and the turntable rotates. We don't know if the microwaves are activated when this happens. The oven works normally when door is closed and time/power are programmed in. It stops at the end of program, but when you open the door, it comes back on.