Breakdown of Ten wiersz został napisany przez znanego autora.
ten
this (m)
znany
known
napisać
to write (perfective)
autor
author
Questions & Answers about Ten wiersz został napisany przez znanego autora.
Why is it znanego autora after przez if przez requires the Accusative case?
You are right that przez requires the Accusative case to show the agent (who performed the action). Because autor (author) is a masculine personal noun, its Accusative form is identical to its Genitive form, resulting in znanego autora instead of a typical Accusative ending.
Why do we use został for 'was' instead of był?
In Polish passive sentences, the helping verb depends on whether the action is finished. został is used with perfective, completed actions like napisać (to write completely). If the writing was an ongoing or repeated process, you would use był with an imperfective verb instead.
Why does the participle napisany end in -y?
Passive participles act like adjectives, so they must match the subject in gender, number, and case. The subject here is ten wiersz (this poem), which is a masculine noun in the Nominative case, so the participle takes the basic masculine singular ending -y.
I learned earlier that przez means 'through'. Does it mean 'by' here?