What is meant by work function (2)
Minimum energy required by an electron to escape from (1) a metal surface (1)
What is meant by ionisation energy? (2)
Minimum energy required to remove an electron from an atom (1)
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What is meant by work function (2)
Minimum energy required by an electron to escape from (1) a metal surface (1)
What is meant by ionisation energy? (2)
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)
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?
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?
The lowest energy state of an atom
Explain the difference between excitation and ionisation (2)
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)
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
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