The bachelor thesis in physics comprises 12 or 8 credits and lasts two months or 6 weeks (depending on the chosen program, i.e. BSc 180, 150 or 120). It is written in the 6th semester of the Bachelor's programme.
An information event is organized at regular intervals, here possible topics for Bachelor and Master theses are presented. Many of the research groups have also set up websites on which they present selected suggested topics or just pass by and ask within the research groups.
A list of suggested topics for bachelor theses can be found here.
You will find the form "Registration Bachelor Thesis" on the page forms and information sheets