Well Placed Sensor
It is located with a clear, unobstructed view of the space around it.
Could be placed better
As you can see, the sensor is placed too close to its fixture, preventing motion on the other side of the fixture from being observed.
Poor sensor placement
There is a sensor on the other side of this fixture, which is not even visible from the hallway. The sensor can’t see anything and is not placed in a location where it can properly do its job. It cannot detect motion due to its position.