CAIE A-Level Physics 11 Particle Physics

Practise analysing atomic and nuclear structure, scattering, isotopes, radiation, decay equations, quark composition, leptons and nuclear mass units.

Exam points

interpret alpha-scattering evidence and nuclear-atom structure
determine nuclide composition, isotopes, notation, charge and conserved quantities
analyse alpha and beta radiation, antiparticles, neutrinos, energy spectra and decay equations
use quark composition and charge to classify hadrons and explain beta decay
distinguish fundamental leptons from composite particles and use u for nuclear mass

Covered syllabus points

11.1 Atoms, nuclei and radiation 11.2 Fundamental particles

[Maximum number: 10]

Fig. 6.1 shows four alpha particles W, X, Y and Z moving towards a gold nucleus that is in thin gold foil.

Fig. 6.1 (not to scale)

(a)

The paths of particles X and Z are shown.

Complete Fig. 6.1 to show possible paths for particles W and Y.

[ 3 ]

(b)

Describe what may be inferred about the structure of an atom from the path of particle X .

[ 1 ]

(c)

When a beam containing many alpha particles is incident on thin gold foil, nearly all of the alpha particles follow paths that are similar to the path of particle Z .

Describe what may be inferred from this about the structure of an atom.

[ 1 ]

(d)

State the mass and the charge, in terms of the atomic mass unit u and the elementary charge e, of an alpha particle.

\begin{array}{r} \text { mass }=\ldots \ldots \ldots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ u ~ \\ \text { charge }=\ldots \ldots \ldots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ e ~ \\ \text { [2] } \end{array}

[ 2 ]

(e)

There are two types of hadron.

The hadrons that are in alpha particles are each composed of three quarks.

[ 3 ]

(i)

State the name of this type of hadron.

[ 1 ]

(ii)

Show, by reference to their constituent quarks, that the hadrons in an alpha particle have charges of either zero or +1 e.

[ 2 ]

charge on up quark $=(+) \frac{2}{3}(e)$ and charge on down quark $=-\frac{1}{3}(e)$

C1

(proton is up up down and neutron is up down down)
$\left(2 \times \frac{2}{3}\right) e-\left(1 \times \frac{1}{3}\right)=1 e \text { and }\left(1 \times \frac{2}{3}\right) e-\left(2 \times \frac{1}{3}\right) e=0$

A1

[Maximum number: 6]

(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}

[ 3 ]

(i)

State what particle is represented by X .

[ 1 ]

$\beta^{-}$ (particle) or electron

B1

(ii)

Compare the nucleon numbers of Q and R.

[ 1 ]

(iii)

Compare the charges of Q and R.

[ 1 ]

[Maximum number: 7]

(a)

Describe the structure of an atom of uranium-238, $\stackrel{238}{92} \mathrm{U}$ .

[ 2 ]

(b)

The decay of uranium-238 is shown by the equation

{ }_{92}^{238} \mathrm{U} \rightarrow{ }_{90}^{234} \mathrm{Th}+\mathrm{X} .

For nucleus X , calculate the ratio, in $\mathrm{Ckg}^{-1}$ , of $\frac{\text { charge }}{\text { mass }}$ .
ratio = $\mathrm{C} \mathrm{kg}^{-1}$

[ 3 ]

charge =2 e
$\left(=2 \times 1.60 \times 10^{-19} \mathrm{C}\right)$

C1

mass =4 u
$\left(=4 \times 1.66 \times 10^{-27} \mathrm{~kg}\right)$

C1

ratio $=\left(2 \times 1.60 \times 10^{-19}\right) /\left(4 \times 1.66 \times 10^{-27}\right)$ $=4.8 \times 10^{7} \mathrm{C} \mathrm{~kg}^{-1}$

A1

(c)

Two particles P and Q each consist of three quarks. These quarks are up (u) or down (d) quarks.

Particle P has no overall charge.
Particle Q has an overall charge of +2 e, where e is the elementary charge.
State the quark composition of:

[ 2 ]

(i)

particle P

[ 1 ]

(ii)

particle Q.

[ 1 ]

[Maximum number: 6]

(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.

[ 4 ]

(i)

For nuclei P and Q , compare:
- the number of protons
- the number of neutrons.

[ 2 ]

(ii)

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 ]

(iii)

State the name of another particle that must be emitted from nucleus Q in addition to the $\beta^{-}$ particle.

[ 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 ]

All question bank results loaded

Covered syllabus points

11. Particle physics question 1

Question (a)

Question (b)

Question (c)

Question (d)

Question (e)

Question (i)

Question (ii)

11. Particle physics question 2

Question (a)

Question (b)

Question (i)

Question (ii)

Question (c)

Question (i)

Question (ii)

Question (iii)

11. Particle physics question 3

Question (a)

Question (b)

Question (c)

Question (i)

Question (ii)

11. Particle physics question 4

Question (a)

Question (i)

Question (ii)

Question (iii)

Question (b)