During β+\beta^+β+ decay inside a proton-rich nucleus, an up quark transforms into a down quark, emitting two leptons. One of these leptons is deflected by a uniform electric field, while the other is undeflected. What is the identity of the undeflected lepton?
positron
electron neutrino
electron antineutrino
electron
90 exam-style questions on OCR A A Level Physics Nuclear and particle physics, covering The nuclear atom, Fundamental particles, Radioactivity, and Nuclear fission and fusion. Each one has a worked solution and a mark scheme showing where the marks go.