A-LevelPhysicsParticle physics9702/21 · May/June 2019 · Q75 Marks

One of the results of the α-particle scattering experiment is that a very small minority of the α-particles are scattered through angles greater than 90°.

(a)State what may be inferred about the structure of the atom from this result.[2]
(b)A hadron has an overall charge of +e, where e is the elementary charge. The hadron contains three quarks. One of the quarks is a strange (s) quark.
(b)(i)State the charge, in terms of e, of the strange (s) quark.[1]
(b)(ii)The other two quarks in the hadron have the same charge as each other. By considering charge, determine a possible type (flavour) of the other two quarks. Explain your working.[2]

Mark scheme

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

[1] nucleus is charged
[1] the mass is concentrated in (very small) nucleus or the majority of the mass is in (very small) nucleus
[1] -(1/3)e
[1] 2q - (1/3)e = e so q = (2/3)e
[1] up/u (quarks) (allow charm or top quarks)

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Topic: Particle physics, A-Level Physics (syllabus 9702). Structured question, 5 marks.
Source: A-Level Physics, May/June 2019 Paper 2 Variant 1, question 7.

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