International A Level (IAL)PhysicsEdexcelExam Questions5. Thermodynamics, Radiation, Oscillations & CosmologyRadioactivity Decay

Radioactivity Decay (Edexcel International A Level (IAL) Physics): Exam Questions

Exam code: YPH11

52 mins12 questions

Medium

Hard

3 marks

Cobalt‐60 is a source of gamma radiation. Gamma radiation can be used to sterilise medical equipment.

i) Complete the nuclear equation for the decay of cobalt-60 to nickel.

${}_{27}^{60}{Co} \to {}_{\dots \dots}^{\dots \dots}{Ni} + {}_{\dots \dots}^{\dots \dots}β^{-} + {}_{0}^{0}{\bar{v}}_{e}$

(2)

ii) Suggest why the majority of the energy released is shared between the β⁻ particle and the antineutrino.

(1)

How did you do?

3 marks

The activity of a cobalt‐60 source is 4.07 × 10¹⁴Bq initially.

When used for sterilising, the source is replaced when the activity drops below 1.85 × 10¹⁴Bq.

Calculate the time in years until the source should be replaced.

half-life of cobalt‐60 = 5.27 years

1 year = 3.16 × 10⁷ s

Time until source should be replaced = .........................years

How did you do?

3 marks

When in use the cobalt-60 source is shielded with lead. The graph shows how the transmission of γ-radiation depends upon the thickness x of the lead shielding.

q19c-wph15-05-oct-2021-edexcel-int-as-and-a-level-phy

The count rate from a source must be reduced from 4.0 × 10¹⁴Bq to 1.2 × 10¹⁴Bq.

Deduce whether lead shielding of thickness 1.0 cm would be sufficient to achieve this.

How did you do?

Was this exam question helpful?

5 marks

A pacemaker is a device used to regulate a person’s heart rate.

Some of the first electronic pacemakers used an isotope of plutonium, Pu-238, as the power source.

Pu-238 decays by alpha emission.

Show that the energy released when a nucleus of Pu-238 decays into a nucleus of uranium is about 5.6 MeV.

	Mass/u
Plutonium nucleus	237.999089
Uranium nucleus	233.991578
α-particle	4.001506

How did you do?

3 marks

Another source that was used in early pacemakers was promethium-147. This emits β-particles. The energy spectrum for the β-particles is shown.

q19c-wph15-05-june-2021-edexcel-int-as-and-a-level-phy

The graphs below show how the range of beta particles depends on the beta particle energy, for different materials.

q19c-1-wph15-05-june-2021-edexcel-int-as-and-a-level-phy

It is suggested that a layer of polyethylene, of thickness 0.5 cm, would be able to absorb all the beta particles emitted from a promethium-147 source.

Comment on this suggestion.

How did you do?

Was this exam question helpful?

2 marks

Protactinium, $Pa$ , is one of the products in the decay series of uranium-238, ${}_{92}^{238}U$ . ${}_{92}^{238}U$ decays to thorium, $Th$ , by emitting an alpha particle. $Th$ then decays to $Pa$ and then to a different isotope of uranium, ${}_{92}^{234}U$ .

Determine the number of $α$ particles and $β$ particles emitted during this process to complete the nuclear equation.

${}_{92}^{238}U \overset{}{\to} {}_{92}^{234}U + . . . . \times {}_{. . . .}^{. . . .}α + . . . . \times {}_{. . . .}^{. . . .}β$

How did you do?

2 marks

The diagram shows the apparatus used by a teacher to demonstrate the decay of protactinium.

Protactinium is produced in a sealed plastic bottle containing a liquid containing a uranium salt. When the bottle is shaken, the protactinium dissolves in the solvent and floats above the liquid containing uranium and thorium.

A sealed bottle with uranium and protactinium layers beside a GM tube linked to a counter for measuring count rate.

The count rate is measured using a Geiger-Müller (GM) tube connected to a counter at intervals of 1.0 minutes for 6.0 minutes. The time intervals are measured using a stopwatch.

Describe how to determine the corrected count rate for the sample.

How did you do?

4 marks

The table shows the corrected count rate $C$ for the sample.

$t$ / $\min$	$C$ / $s^{- 1}$
0	128
1.0	71
2.0	39
3.0	22
4.0	11
5.0	8
6.0	3

The graph shows how $\ln C$ varies with time.

Graph of ln(C) versus time in minutes, showing data points forming a roughly straight decreasing line from about 5 to 1 over 0–6 minutes

Determine the half-life of the protactinium.

How did you do?

3 marks

A student suggests that the results would have been more accurate if a data logger had been used to record the data.

Assess the student’s suggestion.

How did you do?

Was this exam question helpful?