AQA A LEVEL PHYSICS PAPER 1
1.What is meant by work function (2): Minimum energy required by an
electron to escape from (1) a metal surface (1)
2.What is meant by ionisation energy? (2): Minimum energy required to
remove an electron from an atom (1) from the ground state (1)
3.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 over- come work function and therefore have less KE(1)
Maximum KE = Energy of photon - work function ø (1)
4.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)
5.What is meant by the ground state?: The lowest energy state of an atom
6.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
7.Explain why only photons of certain frequencies cause excitation (4):
dis- crete energy levels (1)
Electrons need to absorb a DISCRETE amount of energy to move to a
higher energy level (1)
1/
7
, 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)
8.Explain how excitation takes place in a fluorescent tube: Electrons
flow through the tube to the applied PD causing a current to flow
(1)
Electrons collide with mercury atoms in the tube (1)
This raises electrons in the mercury atom to a higher energy level (1)
9.What is the purpose of coating in a fluorescent tube?: UV/ High energy
photons emitted from mercury atoms when the electrons in the atom
de-excite (1) High energy photons absorbed by the coating (1)
Coating emits photons in the visible spectrum (1)
10.What happens when annihilation occurs? (2): particle and an anti-
particle collide and cease to exist (1)
Their mass is released as energy in the form of a pair of gamma photons
(1)
11.How does the strong nuclear force between two nucleons vary with
the separation of the nucleons? (3): repulsive at < 0.5 fm (1)
attractive from 0.5 to 3 fm (1)
above 3 fm, force 0 (1)
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