CAIE A-Level Physics 11.2 Fundamental Particles

Practise classifying quarks, leptons, baryons and mesons by charge and composition, using uud and udd structures and distinguishing fundamental particles from hadrons.

Exam points

classify quarks, antiquarks, baryons and mesons by flavour, charge and composition
use uud and udd quark compositions to describe protons, neutrons and beta-decay changes
identify leptons and distinguish fundamental particles from composite hadrons

Covered syllabus points

11.2.1—A quark is a fundamental particle and that there are six flavours (types) of 11.2.2—The charge of each flavour of quark and understand that its respective 11.2.3—That protons and neutrons are not fundamental particles and describe protons 11.2.4—A hadron may be either a baryon (consisting of three quarks) or a meson 11.2.5—The changes to quark composition that take place during β– and β+ decay 11.2.6—That electrons and neutrinos are fundamental particles called leptons

[Maximum number: 4]

(a)

State the name of the class (group) of fundamental particles that contains a neutrino.

[ 1 ]

(b)

A hadron P has a charge of +1 e, where e is the elementary charge. The hadron P is composed of a down antiquark and only one other quark.

[ 2 ]

(i)

Identify a possible flavour for this other quark.

[ 1 ]

(ii)

State what type of hadron is P .

[ 1 ]

(c)

Nucleus Q undergoes radioactive decay to form nucleus R, emitting an antineutrino and another particle X, as shown in the decay equation.

Q \rightarrow R+X+\bar{v}

[ 1 ]

(i)

Compare the charges of Q and R.

[ 1 ]

[Maximum number: 3]

(a)

Nucleus P and nucleus Q are isotopes of the same element.
Nucleus Q is unstable and emits a $\beta^{-}$ particle to form nucleus R.

[ 1 ]

(i)

When nucleus Q decays to form nucleus R, the quark composition of a nucleon changes. State the change to the quark composition of the nucleon.

[ 1 ]

(b)

A hadron consists of two charm quarks and one bottom quark.

Determine, in terms of the elementary charge e, the charge of the hadron.
charge = e

[ 2 ]

[Maximum number: 3]

(a)

Describe two differences between the decay of a nucleus that emits a $\beta^{-}$ particle and the decay of a nucleus that emits a $\beta^{+}$ particle.
1.
2.

[ 2 ]

$\beta^{-}$ emission: neutron changes to proton (+ beta-/electron)

and

$\beta^{+}$ emission: proton changes to neutron ( + beta $^{+}$ /positron)

B1

$\beta^{-}$ emission: (electron) antineutrino also emitted

and

$\beta^{+}$ emission: (electron) neutrino also emitted

B1

(b)

In a simple quark model there are three types of quark. State the composition of the proton and of the neutron in terms of these three quarks.
proton:
neutron:

[ 1 ]

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Covered syllabus points

11.2 Fundamental particles question 1

Question (a)

Question (b)

Question (i)

Question (ii)

Question (c)

Question (i)

11.2 Fundamental particles question 2

Question (a)

Question (i)

Question (b)

11.2 Fundamental particles question 3

Question (a)

Question (b)