“Who are you known to”

My English teacher asked me to construct the passive voice of the sentence "Who knows you?". Then, I could immediately make up the sentence "To whom are you known?". My English teacher said that it was absolutely correct.

But she constructed another sentence: "Who are you known to?". I could understand that the sentence is grammatically correct as the preposition "to" is at the end now, and the interrogative pronoun "who" is not a prepositional object. But still I could not appreciate that the meaning of the second sentence should be as clear as the first one. How should I understand "1. Who, are you know to?" and "2. Who are you, known to?"? I could not make out the meaning of the sentence "Who are you known to?".

Please explain the reasoning leading to the right interpretation.

who knows you?
To whom are you known?
Who are you known to

The passive form is"By whom are you known?"; there is a confusion between the verbal forms " to be known by" and "to be known to somebody" (ngram, ngram). In this second form the verb is not transitive and it does not mean "identify"; instead it is intransitive and means "have understanding or knowledge" (SOED (III 9)).

• It has been known to them for some time that the earth is not flat.
• Those facts are known to the owner.
• — To whom are those facts known? — To the owner.

The rule of passage from the active to the passive form is given in the following diagram.

From A comprehensive grammar of the English language, § 3.65