IGCSEPhysicsCIETopic Questions5. Nuclear Physics5.2 Radioactivity

Radioactivity (CIE IGCSE Physics)

Topic Questions

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1a1 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]

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1b2 marks

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

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1c4 marks

Radioactive emissions have differing characteristics. One characteristic is their ionising effect.

   
Complete the statement about ionisation, using words from the box. The words can be used once, more than once or not at all.

  

electrons      negatively      neutrons      positively      neutrally      protons

  
When atoms are ionised,

............................... may be removed,

leaving ............................... charged atoms (ions),

or ............................... may be gained,

forming ............................... charged atoms (ions).

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1d2 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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2a2 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]

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2b3 marks

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

 
feb-march-2018-42-q11

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2c2 marks

Extended

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

[1]

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3a1 mark

Define the term "half-life".

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3b3 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. 

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3c5 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]

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3d1 mark

Extended

 

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

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4a2 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.

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4b2 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

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4c5 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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5a3 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    

     

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5b3 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.

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5c2 marks

Extended

 

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. 

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5d2 marks

Extended

 

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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1a3 marks

A radioactive nucleus of carbon decays to a nucleus of nitrogen by emitting a particle.

 
Complete the nuclide equation and state the name of the particle.

 
straight C presubscript 6 presuperscript 14 rightwards arrow straight N presubscript 7 presuperscript 14 plus straight X presubscript... end presubscript presuperscript... end presuperscript

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1b2 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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24 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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3a1 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 

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3b1 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

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3c3 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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4a2 marks
A radioactive substance decays by emitting an α-particle.
   

The nuclide notation for an α-particle is

   
straight alpha presubscript 2 presuperscript 4
    
(i)
State the term given to the number 4, written in the nuclide notation.
[1]
   
(ii)
State the term given to the number 2, written in the nuclide notation.
[1]

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4b4 marks

Fig. 12.1 shows the decay curve for a radioactive material.

  
screenshot-2022-10-20-at-12-11-24
  
(i)
Use information from the graph in Fig. 12.1 to determine the half-life of the material. Clearly show how you used the graph to obtain your answer.
 
 
 half-life = ...................................................... minutes [3]
 
(ii)
Another radioactive material with the same half-life has an initial count rate of 600 counts/min. On Fig. 12.1 sketch the decay curve for this material.
[1]

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5a4 marks

Astatine-210 is a radioactive material. The nucleus of astatine can be represented by the symbol shown.

A presubscript 85 presuperscript 210 t

Complete the table to describe the nucleus of astatine-210.

 
type of particle number of particles charge on particle
neutron    
    positive

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5b5 marks

Astatine-210 has a half-life of 8 hours.

 
(i)
The count rate of a sample of astatine-210 is measured over 24 hours.
 
On Fig. 12.1, sketch a line to show how the count rate changes over the 24 hours.
 
cie-2019-18
[2]
(ii)
The mass of a sample of astatine-210 is 0.500 kg.
 
Calculate how long it takes for 0.375 kg of the sample to decay.
 
 
decay time = ............................................... hours [3]

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6a3 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]

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6b4 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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1a3 marks

The isotope hydrogen-1 has a proton number of 1 and a nucleon number of 1.

 
Two isotopes of helium are helium-3 and helium-4.

 
Helium-3 has a proton number of 2 and a nucleon number of 3.

 
Helium-4 has a nucleon number of 4.

 
Complete Table 11.1 for neutral atoms of these isotopes of helium.

   table3

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1b3 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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2a3 marks

This notation represents the nucleus of a neutral atom of carbon-14.

 straight C presubscript 6 presuperscript 14

State the number of:

 
(i)
protons in the nucleus of an atom of carbon-14
[1]
(ii)
electrons orbiting the nucleus of an atom of carbon-14
[1]
(iii)
neutrons in the nucleus of an atom of carbon-14.
[1]

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2b3 marks

Carbon-14 is an isotope of carbon. Carbon-12 is another isotope of carbon.

 
Compare the nucleus of carbon-14 with the nucleus of carbon-12.

  
State the similarities and differences.

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2c3 marks

Scientists use carbon-14 to estimate the age of wood that is very old.

 

A very old sample of wood contains 1.0 × 108 carbon-14 atoms.

 

When the sample was new, it contained 8.0 × 108 carbon-14 atoms. The half-life of carbon-14 is 5700 years.

 

Estimate the age of the sample of wood.

 
 
 
 
age of wood = ........................... years

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3a1 mark

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

 

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

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3b1 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 = ........................................................

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3c3 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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4a2 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.

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4b6 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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5a2 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]

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5b5 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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6a3 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. ...........................

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6b2 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

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6c3 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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7a3 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

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7b6 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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8a2 marks

Extended

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

VnHpZL5z_q11a

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8b5 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]

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8c3 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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