<p>1 of 2 Examzone: Student book topic tests mark scheme</p><p>Unit 4 Topic 3 Particle physics</p><p>1 (a) Lots of energy needed (1) to produce the extra mass (1) (b) Conservation of charge (1) Conservation of lepton number (1) Conservation of baryon number (1) (c) They annihilate one another (1) giving rise to g-ray/g photon (1) Energy of g-ray 5 2 3 0.00055 3 930 MeV (1) 5 1.0/1.02/1.023 MeV (1) (Total 9 marks) 2 (a) (i) n 5 udd and p 5 uud (1) _ b2 and vhave no quarks / are leptons / are fundamental (1) (ii) p n (1) 1 b1 1 v [allow e1] (1)</p><p>(b) Baryon and hadron (1) Lepton (1) (c) (i) Antiproton [or anti-up quark, anti-down__ quark] and positron (1) __ __ __ 1 (ii) p 5__ and e 5 11 [accept correct u, d charges for p] (1) 21 __ __ u u d (e1 fundamental / no quarks) [e.c.f. from (b), credit if in (i)] (1) (iii) Zero / neutral (1) (iv) Annihilates (2) [on contact with matter / container / protons / H] OR Not charged: not affected by magnetic fields (2) (Total 12 marks) 3 Charge on strange quark: 21/3 (1) Conservation law: Charge 2 (21) 1 (11) (0) 1 X/by charge conservation (1) X is neutral (1) Meson or baryon: Particle X is a meson (1) Baryon number conservation (0) 1 (11) (11) 1 (0) (1) __ __ OR Discussion in terms of total number of q 1 q 5 5 OR q 2 q 5 3 Composition of X __ __ Is sd [0/3 if not qq](1) Justify S quark: This is not a weak interaction/only a weak interaction can change quark type/this is a strong interaction/strangeness is conserved/ quark flavour cannot change (1) __ __ Justify d quark: X neutral; s 2 1/3; d 1 1/3. [e.c.f. if s 5 2 1/3 in first line.] __ For the third mark accept any q q pair that creates a meson of the charge deduced for __ X above. (1) [The justification for both q and q can be done also by tracking individual quarks]</p><p>158</p><p>Examzone: Student book topic tests mark scheme 2 of 2</p><p>Unit 4 Topic 3 Particle physics (cont.)</p><p>4 Similarity Any 1 from: both nuclear decay products both charged/ionise/damage tissue both have momentum both deflected by electric fields by magnetic fields (1) Differences Any 2 from: b fundamental, a not mass a mass b a positive, b either b a lepton, a composed of hadrons a is He21, b is e1 or e2 (2) [A difference must mention BOTH particles] [If discussing spectrum shape needs given source idea] (Total 3 marks) 5 Meson or bayron: V2 is a baryon [no mark] p is a baryon/need to conserve baryon number (1) Strangeness 3 needs three quarks (1) Composition p is uud V2 is sss All Ks quark-antiquark pairs _ _ __ K2 is us; K1 is us; K0 is ds [all correct, 4] (Total 6 marks) 6 Explanation: Diffraction (1) Molecular/atomic separation &gt;1 nm/de Broglie wavelength (1) Kinetic energy: Use of l 5 h/mv (1) 1 Use of KE 5 _ mv2 OR p2/2m (1) 2 KE 5 9.19.2 3 10223 J [no e.c.f.] (1) Waveparticle duality: Quality of written communication (1) When a wave/particle behaves like / has properties / has characteristics of a particle/wave (1) Neutron is a particle in the (a) nucleus / it has momentum / mass / can collide (1) Neutrons diffract/interfere, a wave-like property. (1) (Total 9 marks)</p><p>159</p>