Nuclear Fusion & Fission (Edexcel International A Level Physics)

Topic Questions

2 marks

Actinium‐225 is a radioactive isotope. It decays to francium by emitting alpha particles.
Actinium‐225 has a short half-life, which makes it suitable for medical applications.

Complete the nuclear equation for this decay.

${}_{89}^{225}{Ac} \to {}_{\dots}^{\dots}{Fr} + {}_{\dots}^{\dots}α$

How did you do?

4 marks

In a radioactive decay, energy is released and the total mass decreases.

Show that the energy released if the mass decreases by 1 u is about 930 MeV.

How did you do?

4 marks

The francium nucleus and the alpha particle move away from each other after the decay.

Explain why the kinetic energy given to the alpha particle is just less than 5.9 MeV.

mass decrease for the decay = 6.35 × 10^–3 u

How did you do?

4 marks

The activity of a sample of actinium‐225 is 7.4 × 10⁷ Bq when it is prepared.

Calculate the number of actinium atoms in the sample 7.0 days later.

half‐life of actinium-225 = 9.9 days

Number of actinium atoms after 7.0 days = ...........................

How did you do?

Did this page help you?

2 marks

Experiments with muons are taking place at Fermilab in the USA to improve our understanding of the standard model.

The muon belongs to the same family of particles as the electron.

State how the muon is classified in the standard model.

How did you do?

2 marks

A muon (μ) can be produced by the decay shown in this nuclear equation.

$π^{-} \to μ^{-} + ν_{μ}$

State the names of the two other particles involved.

How did you do?

3 marks

A website states: “The rest mass of a muon is 106 MeV / c², which is a little over 200 times that of an electron.”

Deduce whether this statement is correct.

How did you do?

7 marks

Muons are stored in a ‘storage ring’ at Fermilab. The website describes the ring as having a circumference of 44.7 m and using a magnetic field of flux density 1.45 T.

The website claims that this enables the storage ring to confine muons with a momentum of 3.10 GeV / c.

Explain why the unit GeV / c is a valid unit for momentum.

(2)

ii)

Deduce whether the website’s claim is correct.

muon charge = −1.6 × 10⁻¹⁹ C
3.10 GeV / c = 1.65 × 10^–18 N s

(3)

iii)

Stationary muons are unstable and have a mean lifetime of a few microseconds.

Explain why muons in the ring are observed to have a much greater mean lifetime.

(2)

How did you do?

Did this page help you?

	Download	View
Medium
Hard

Nucleus	Mass/u
²²⁸Th	228.02873
²²⁴Ra	224.02021
⁴α	4.00260

	Mass/GeV/c²
${}_{92}^{236}U$	219.8750
n	0.93956
p	0.93827