On the basis of the girl's police complaint lodged on September 5, Brij Mohan alias Saurabh was arrested on Tuesday, police said.
The girl, a student of Gargi college, claimed that Mohan had also made an obscene video of her with which he was trying to extort money from her.
"Mohan was known to the girl since her school days. He had developed physical relation with her and filmed the act with a hidden camera. With the help of that obscene clip, he was trying to extort money from her," a police official said.