The dog bit the boy. The boy was bitten by the dog.
I wrote the note. The note was written by me.
It can be hard in some cases to tell whether it's passive or an adjective. For example: I was tired - it's cleary an ajective here. But: I was tired out by that long hike. You can say "The long hike tired me out" so it sure lo
You can say "The long hike tired me out" so it sure looks passive, but I'd still call it a desciption of my state (and therefore an adjective), rather than passive.
If tired is an adjective in The long hike tired me out, which of the other words is the verb? hike? me? out?
It certainly seems to be one of those ambiguous cases where either the "state" interpretation or the "action upon the subject" interpretation is possible.
I was surprised/frightened. The door was closed/locked. Fran and Tom were married.
An animate agent in a by clause pushes us strongly toward a passive interpretation, but an inanimate can go either way.