Radioactivity (Cambridge O Level Physics)

Exam Questions

3 hours42 questions
1a
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3 marks

Fig. 1.1 shows the names of three different processes that take place in different locations.

kNm_CrVo_nuclear-processes

Fig 1.1

Draw one line from each process to the location it takes place.

1b
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2 marks

This passage is about the differences between nuclear fission and fusion.

Tick the correct statements in the table below

7-3-easy-q5b-fission-and-fusion

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2a
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1 mark
Fig. 12.1 shows the nuclide notation for three isotopes of an element.
screenshot-2022-10-27-at-16-54-05
(i)
Describe how the nuclide notation shows that each isotope is of the same element.
[1]
 
(ii)
Describe how the nuclide notation shows the differences between the isotopes.
[1]
2b
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2 marks

Radioactive sources emit radiation when they decay. State the names of three types of radioactive emission.

2c
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2 marks

Polonium-210 has a half-life of 140 days. A sample of polonium-210 has 8.0 × 1010 atoms. Calculate the number of polonium-210 atoms remaining in the sample after 280 days.

   
   
number of atoms = ...................................................... 

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3a
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1 mark

Define the term "half-life".

3b
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3 marks

Complete the sentences.

The particles in _______ radiation have a greater mass than those in _______ radiation.

_______ radiation is a type of electromagnetic radiation and does not have mass. 

3c
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5 marks

Extended

 

Three radioactive sources, X, Y and Z, are in a lab. One emits only alpha radiation, one emits only beta radiation and one emits only gamma radiation.

(i)
Draw a line between the type of radiation and its charge.
screenshot-2023-02-06-at-16-38-06
[2]
 
(ii)

To determine which source emits which type of radiation, a scientist places a positive charge near the sources, as shown in Fig. 1.1.

5-2-3c-e-alpha-beta-gamma-deflection

State the type of radiation coming from each source.
[3]
3d
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1 mark

Suggest one safety precaution the scientist might take the protect herself from the radioactive sources. 

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4a
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2 marks

An iodine isotope I presubscript 53 presuperscript 135 decays beta emission. The daughter particle is an isotope of xenon (Xe).

State the number of each type of particle in a neutral atom of I presubscript 53 presuperscript 135.

4b
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2 marks

Extended

 

Complete the decay equation:

  
straight I presubscript 53 presuperscript 135 space rightwards arrow space straight beta presubscript... end presubscript presuperscript... end presuperscript space plus space Xe presubscript... end presubscript presuperscript... end presuperscript
4c
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5 marks

A factory makes baking paper. In order to keep the baking paper the same thickness, beta radiation is passed through the paper.

A Geiger counter on the other side of the paper measures how much radiation passes through the paper and the rollers change the thickness of paper accordingly (see Fig. 1.1).

5-2-4c-e-paper-roller-beta

(i)
Explain why alpha radiation is not used. 
[2]
 
(ii)
Explain why gamma radiation is not used.
[2]
 
(iii)
A worker bumps into the rollers. The Geiger counter now detects a greater count rate. Describe how the thickness of the paper has changed. 
[1]

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5a
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3 marks

A student records the following data in a table when using a Geiger counter on two radioactive sources at the same.

Complete the table.

   
Source Recorded count rate (counts/s) Background count rate (counts/s) Corrected count rate (counts/s)
Radium 104   100
Americium 25    

     

5b
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3 marks

The half-life of the radium isotope is 30 days. Calculate the count rate from the radium source from part (a) after 60 days.

5c
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2 marks

Another source has an initial activity of A0.

5-2-5c-e-activity-graph-7-5
Fig. 1.1

Use Fig. 1.1 to determine the half-life of the source. 

5d
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2 marks

Medical tracers are radioactive sources that can be inserted into the body to track the movement of blood.

Explain why the isotope from part (c) would be an inappropriate radioactive source for this purpose.

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6a
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2 marks

To ensure the safety of workers in laboratories where radioactive sources are used, describe how radioactive materials

(i)
should be stored,
[1]
(ii)
should be handled.
[1]
6b
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3 marks

Complete the table below for three types of emission from radioactive sources.

 
feb-march-2018-42-q11
6c
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2 marks

State the type of radiation emitted when

(i)

an americium nucleus ( Am presubscript 95 presuperscript 241) decays into a neptunium nucleus (Np presubscript 93 presuperscript 237),

[1] 

(ii)

a phosphorus nucleus (straight P presubscript 15 presuperscript 32) decays into a silicon nucleus ( Si presubscript 16 presuperscript 32).

[1]

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1a
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3 marks

A nucleus of americium-241 has the nuclide notation shown.

 
space presubscript 95 presuperscript 241 A m

(i)
Determine the number of neutrons in a nucleus of americium-241.
 
 

number of neutrons = ........................................................ [1]

 

(ii)
Determine the charge on a nucleus of americium-241.
 
charge = ........................................................ [2]
1b
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2 marks

Americium-241 decays by emitting α-particles.


Put a tick in the box next to each correct statement.

 
square  α-particles are electromagnetic waves.
 
square  α-particles are fast-moving electrons.
 
square  α-particles are helium nuclei.
 
square  α-particles are stopped by a sheet of paper.
 
square  α-particles can pass through 3 cm of aluminium.
1c
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2 marks

Americium-241 has a half-life of 432 years.
A sample contains 16 mg of americium-241.


Calculate the time it takes until only 4.0 mg of americium-241 are left in the sample.

 

time = .............................................. years 

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2
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3 marks

An experiment takes place in a laboratory shielded from all background radiation. A sample of radioactive material is wrapped in aluminium foil of thickness 0.1 mm. A detector of ionising radiation placed 1 cm from the foil records a reading.


A piece of aluminium of thickness 5 mm is placed between the detector and the foil. The detector reading drops to zero.

 
State and explain any type of radiation passing through the aluminium foil.

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3a
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1 mark

Radioactive sources emit α-(alpha), β-(beta) and γ-(gamma) radiations.

 

State which of these types of radiation can pass through paper.

3b
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1 mark

Barium-137 is a radioactive isotope. The nuclide notation for barium-137 is

 
B presubscript 56 presuperscript 137 a
 

Determine the number of neutrons in a nucleus of barium-137.

 
 
number of neutrons = ........................................................
3c
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3 marks

An isotope of barium–137 has a half-life of 3 minutes.

A radioactive source contains 36 mg of this isotope.

Calculate the mass of the isotope that remains in the source after 9 minutes.

 
 
 mass of the isotope remaining = .................................................. mg

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4a
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2 marks

Fig. 10.1 shows a vacuum tube with a radioactive source. The radioactive source emits α-particles, β-particles and γ -rays. There is a very strong magnetic field between the N pole and the S pole of the magnet.

 may-june-2020-42-q10

The lead cylinder has a narrow central hole. State and explain the effect of the lead cylinder.

4b
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6 marks

Extended

Describe the paths of the α-particles, β-particles and γ -rays as they pass through the magnetic field. Explain your answers.

 
(i)
α-particles
[2]
 
(ii)
β-particles
[2]
 
(iii)
γ -rays
[2]

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5a
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2 marks

Radioactive decay may include the emission of:

α-radiation

β-radiation

γ-radiation

(i)
From the list, state the type of radiation which has the greatest ionising effect.
[1]
  
(ii)
From the list, state the type of radiation which has the lowest penetrating ability.
[1]
5b
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5 marks

In a factory, rollers press aluminium metal to make thin foil sheets. An automatic system for controlling the thickness of the foil uses a radioactive source. The automatic system changes the gap between the top and bottom roller. Fig. 12.1 shows the equipment.

q12b
(i)
Use your ideas about the properties of radiation to suggest and explain the type of radiation used.
 
type of radiation: ..........................................................................................
 
explanation: ..........................................................................................
[2]
 
(ii)
The aluminium foil passing the radiation detector is too thin. Describe how this fault affects the reading on the counter.
[1]
 
(iii)
Suggest how the fault in (b)(ii) is corrected. State what happens to the rollers.
[1]
 
(iv)
The source used is strontium-90. A nucleus of strontium-90 can be described as space presubscript 38 presuperscript 90 Sr. State the number of protons in a nucleus of strontium-90.
[1]

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6a
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3 marks

Radon-222 is radioactive. It can be represented as Rn presubscript 86 presuperscript 222.

For a neutral atom of radon-222, state

 
1. the number of protons, ...........................
 
2. the number of neutrons, ...........................
 
3. the number of electrons. ...........................
6b
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2 marks

Extended

A radon-222 nucleus decays by α-particle emission to a polonium (Po) nucleus.

Complete the equation for the decay of radon-222.

 
Rn presubscript 86 presuperscript 222 rightwards arrow
6c
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3 marks

Radon-222 has a half-life of 3.8 days.

At a certain time, a sample contains 6.4 × 106 radon nuclei.

Calculate the number of α-particles emitted by the radon nuclei in the following 7.6 days.

 

 

number = ...........................................................

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7a
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3 marks

The nuclide notation space presubscript straight Z presuperscript straight A straight X describes the nucleus of one type of atom.
Draw a line from each symbol to the correct description for that symbol.

q12a

7b
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6 marks
(i)

One radioactive isotope has a half-life of 6.0 years.

A sample of this isotope has a mass of 12 mg.

Calculate the mass of this isotope that remains in the sample after 18 years.

 

 

mass remaining = .................................................... mg [3]

(ii)

The sample decays by emitting a β-particle.

Describe the nature of a β-particle.

 [2]

(iii)

Describe how the nucleus of the isotope changes due to the emission of a β-particle.

 [1]

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8a
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2 marks

A radioactive nucleus of uranium-235 decays to a nucleus of thorium and emits an α-particle.
Complete the equation.

VnHpZL5z_q11a
8b
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5 marks

A nucleus of uranium-235 undergoes nuclear fission in a reactor.

 
(i)
State what is meant by nuclear fission.
[1]
 
(ii)
Suggest why a nuclear reactor is surrounded by thick concrete walls.
[2]
 
(iii)

State one environmental advantage and one environmental disadvantage of using a fission reactor to generate electrical energy in a power station.

[2]
8c
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3 marks

The thorium produced by the decay in (a) is also radioactive and has a half-life of 26 hours.

At a certain time, a pure sample of this isotope initially contains 4.8 × 109 atoms.

Calculate the number of atoms of this sample that decay in the following 52 hours.

 

 

number = ...........................................................

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9a
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6 marks

Table 10.1 contains details of the nature and some properties of alpha, beta and gamma emissions.

Table 10.1

  alpha beta gamma
nature 2 protons and 2 neutrons    
charge   negative  
penetrating power   stopped by 5mm of aluminium   

Complete Table 10.1 by filling in the missing details.

9b
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5 marks

Surgical instruments in sealed plastic bags are placed in thin plastic boxes. A conveyor belt takes the boxes close to a cobalt-60 source which sterilises the instruments.

This is shown in Fig. 10.1.

q10b-cie-ol-physics-paper-2-2021-sq

Fig. 10.1 (viewed from above)

The cobalt-60 source is a radioactive isotope of cobalt that emits gamma-radiation

(i)
Describe what is meant by the term isotope.

[2]

(ii)
Suggest a property of gamma-radiation that enables it to sterilise the instruments in the bags in the boxes.

[1]

(iii)

State why a source emitting only alpha-radiation cannot be used in this way.

[1]

(iv)
The half-life of cobalt-60 is 5.3 years.

Explain why a source with a half-life of 5.3 minutes is unsuitable for use in this application.

[1]

9c
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4 marks

Geiger and Marsden performed an experiment in which alpha-particles were fired at a thin film of gold.
 

(i)
Fig. 10.2 shows an alpha-particle passing close to the nucleus of a gold atom.

q10c-cie-ol-physics-paper-2-2021-sq
Fig. 10.2
Explain why the alpha-particle is deflected

. [2]

(ii)
In the experiment, most of the alpha-particles pass straight through the foil without deflection. 

 Explain, using ideas about the structure of the atom, why this happens.

. [2]

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10a
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3 marks

Fig. 9.1 shows the main parts of a nuclear reactor.

q9-cie-ol-physics-specimen-paper-2-sq

Fig. 9.1

The fuel rod contains uranium-235, which can undergo nuclear fission.

Describe the process of nuclear fission that occurs in the fuel rod.

Your description should include the role of neutrons in the process.

10b
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2 marks

Explain what happens as a control rod is moved out of the reactor core.

10c
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1 mark

The nuclear reactor releases energy at a steady rate. 

By referring to neutrons, describe what is happening to achieve this steady rate.

10d
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2 marks

Explain the purpose of the moderator in the nuclear reactor.

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1a
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2 marks

When uranium-235 (space presubscript 92 presuperscript 235 straight U) is bombarded with a neutron, it forms an isotope of caesium (Cs) and an isotope of rubidium (Rb). 

Complete the nuclide notation for this reaction.

 
straight U presubscript 92 presuperscript 235 space plus space straight n presubscript square presuperscript square space rightwards arrow Cs presubscript square presuperscript 144 space plus space Rb presubscript 37 presuperscript square space plus space 2 straight n presubscript square presuperscript square
1b
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3 marks

State and explain the process shown by the equation in (a)

1c
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3 marks
(i)
Describe and give a reason for the difference between the mass of the products and the reactants in the reaction from part (a)
[2]
 
(ii)
State the energy transfer that takes place in the products of the reaction from part (a).
[1]

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2a
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1 mark

There are three naturally occurring isotopes of hydrogen: hydrogen-1, hydrogen-2 and hydrogen-3.

Hydrogen-1 is the simplest nuclide containing only one proton. Each isotope of hydrogen is represented by the symbol H.

Write down the symbols, using nuclide notation, for:

hydrogen-1 ...................................

hydrogen-2 ...................................

hydrogen-3 ...................................

2b
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5 marks

Extended

In a fusion reactor, a nucleus of hydrogen-2 and a nucleus of hydrogen-3 undergo fusion.

 
(i)
State what is meant by nuclear fusion.
[2] 
(ii)
The fusion reaction produces a free neutron and one other particle.
 
Write down, using nuclide notation, the equation that represents this reaction.
[3]

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3a
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4 marks

Fig 1.1 shows a neutron colliding with a nucleus of uranium-235, producing a number of products.

5-1-5a-h-uranium-235-fission-chain-reaction-sq-igcse

(i)
Name the process shown in the diagram.
[1]
(ii)
Complete, using nuclide notation, the equation that represents the reaction shown in Fig 1.1.
 

fission-reaction

[3]

3b
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3 marks

Explain how the process shown in Fig 1.1 can lead to a chain reaction.

3c
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2 marks

This process releases energy.


Explain the energy transfer taking place in this reaction.

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4
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4 marks

A radiation detector in a laboratory records a reading of 10 counts/min. There are no radioactive samples in the laboratory.

 
(i)
Explain why the radiation detector records a reading and suggest a possible source.
[2]
 
(ii)

Carbon-14 has a half-life of 5700 years. There are atoms of carbon-14 in all living organisms.

 

An archaeologist digs up some ancient wood. In the same laboratory as in (b)(i), a sample of this ancient wood gives a reading of 20 counts/min. An equivalent sample of living wood gives a reading of 80 counts/min. It is suggested that the age of the ancient sample is 11 400 years.

 

Do a calculation to check whether this suggestion is correct.

[4]

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5
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4 marks

Fig.12.1 shows a radioactive source placed close to a radiation detector and counter. The detector can detect α, β and γ radiation.

feb-march-2018-32-q12

The radioactive source emits β-particles only.

 
Describe how you could show that the source emits β-particles only.
As part of your answer, you may draw on Fig.12.1 and add any other apparatus you may need.

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6a
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1 mark
A teacher carries out two experiments at the same time.
 

In the first experiment the count rate for a sample of a radioactive isotope is measured every 30 seconds for 6 minutes.


The results are shown in Table 12.1.

screenshot-2022-10-14-at-09-35-36

Estimate the half-life of the radioactive isotope. Use the information in the table.

 
half-life = ...................................................... minutes 
6b
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1 mark

In the second experiment the teacher repeats the procedure with another sample of the same radioactive isotope. The mass of the second sample is greater than that of the first sample.

 
Suggest a value for the count rate for this sample at the start of the experiment.

 
count rate = ...................................................... counts/second
6c
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3 marks

One type of particle emitted during radioactive decay is an α-particle (alpha particle).

Describe:

  
(i)
the nature of an α-particle

[1]

(ii)
the ionising ability of an α-particle

[1]

(iii)
the penetrating ability of an α-particle.

[1]

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7a
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3 marks

State the type of radioactive emission that causes

 
(i)
the proton number of a nuclide to increase by 1,
[1]
(ii)
the nucleon number of a nuclide to decrease by 4,
[1]
(iii)
no change in the proton number and no change in the nucleon number of a nuclide.
[1]
7b
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4 marks

The isotope radon-220 is radioactive and it decays by α-particle emission.

 
(i)

Fig. 11.1 shows a beam of α-particles entering the electric field between two charged plates.

q11b

On Fig. 11.1, sketch the path that the beam of α-particles follows in the electric field.

[1]

 
(ii)

The half-life of radon-220 is 56 s.

A sample of this isotope contains 7.2 × 106 atoms.

Predict the number of α-particles that the radon-220 in the sample emits in the next 168 s.

 

 

number of α-particles emitted = ...........................................................[3]

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