An experimental physicist investigates how the count rate of alpha particles detected by a Geiger-Müller tube changes as the distance between the americium-241 source and the detector's window is varied.
State the independent variable in this investigation.
81 exam-style questions on Edexcel GCSE Physics 6.1 Atomic structure and isotopes, covering 6.1.1 Structure of the atom, 6.1.2 Isotopes: atomic and mass number, 6.1.3 Sub-atomic particles: masses and charges, and 6.1.4 Electron orbits and energy changes. Each one has a worked solution and a mark scheme showing where the marks go.