6 exam-style questions on AQA A Level Physics The discovery of the electron (A-level only), covering Cathode rays (A-level only), Thermionic emission of electrons (A-level only), Specific charge of the electron (A-level only), and Principle of Millikan's determination of the electronic charge, $e$ (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.