aqa a level physics paper 1

What is meant by work function (2) - answer-Minimum energy required by an electron to escape from (1) a metal surface (1) What is meant by ionisation energy? (2) - answer-Minimum energy required to remove an electron from an atom (1) from the ground state (1) Why do emitted electrons have a kinetic energy that varies up to a maximum value? (4) - answer-Energy of a photon is fixed/constant (1) Energy is required for electrons to overcome work function ø (1) Electrons deeper into/below the surface of the metal require more energy to overcome work function and therefore have less KE(1) Maximum KE = Energy of photon - work function ø (1) Explain how (bright ring) diagram is evidence of the wave-particle duality of electrons? - answer-Diffraction pattern maxima/minima (bright and dark areas) (1) Diffraction is a property of waves- proves wave-behaviour of electrons (1) What is meant by the ground state? - answer-The lowest energy state of an atom Explain the difference between excitation and ionisation (2) - answer-An electron receives a discrete amount of energy for BOTH (1) Excitation promotes an electron to a higher energy level Ionisation is when an electron receives enough energy to leave the atom Explain why only photons of certain frequencies cause excitation (4) - answer-discrete energy levels (1) Electrons need to absorb a DISCRETE amount of energy to move to a higher energy level (1) Photons need to have a certain frequency to provide this energy, because E=hf (1) interaction is a 1:1 reaction all of the photon's energy is absorbed (1) Explain how excitation takes place in a fluorescent tube - answer-Electrons flow through the tube to the applied PD causing a current to flow (1) E