A-LevelPhysicsParticle physics9702/21 · Oct/Nov 2019 · Q74 Marks

7 (a) The decay of a nucleus ¹⁸₃₅Ar by β⁺ emission is represented by ¹⁸₃₅Ar → X + β⁺ + Y. A nucleus X and two particles, β⁺ and Y, are produced by the decay. State:

(a)(i)the proton number and the nucleon number of nucleus X proton number = .................................................... [1] nucleon number = .................................................... [1][1]
(a)(ii)the name of the particle represented by the symbol Y. [1][1]
(b)A hadron consists of two down quarks and one strange quark. Determine, in terms of the elementary charge e, the charge of this hadron. charge = .................................................... [2][2]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.

[A1] proton number = 17; and nucleon number = 35
[B1] (electron) neutrino
[C1] d/down (quark charge) is -1/3(e); or two d/down (quark charges) is –2/3(e); or s/strange (quark charge) is -1/3(e)
[A1] charge = –1/3(e) –1/3(e) –1/3(e); = -1(e)

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