Choose 3 problems from the PDF. Attempt each without looking at any solution or external resource. Time yourself. If you don't finish, stop. Record where you got stuck.

Wave optics (interference, diffraction, polarization) and geometrical optics.

Don't just look for the answer. Study the "Chinese style" of problem-solving, which often involves elegant mathematical shortcuts.

A platform used by higher-level physics students and Olympiad veterans. It is an excellent place to ask for difficult CPhO problem derivations and find high-level resources. 3. University and Coaching Websites