Extracurriculars for physicsWatch
None of it is necessary though and universities (especially Oxford/Cambridge) realise not all applicants will have equal opportunities to take part in such extracurriculars. The main thing you can do to make your application stand out is to prepare for the PAT (for Oxford) and try to do as well as possible in that, as that will likely be the primary factor considered by Oxford when shortlisting applicants.
Sinnoh is currently studying physics and might be able to advise what, if anything, they did extracurricularly?
I think mine should serve as an example that you don't need to do a whole lot. I mentioned two books on the subject that I'd read and why they appealed to me, I talked about my doing astronomy GCSE as an EC (really only talked about the cosmology bits) and I made a bit of a pathetic attempt to relate this article I'd written for my school's history magazine to the subject.
You don't need to cram your personal statement to the brim (get some line breaks in there, makes it so much easier to read) and you don't always need "evidence" about why you're interested in the first place. 6 months before I sent my application I was pretty sure I'd do aeronautical engineering.
Some people in the year below me started up a science magazine, which is probably a bit more impressive...
But basically don't just say you did a thing, talk about why it matters