IGCSE Physics 0625 — Topic 5: Nuclear Physics — Paper 2 (MCQ) Cambridge Challenge

Question 1

In the alpha scattering experiment, a beam of alpha particles is directed at a thin gold foil. Most alpha particles pass straight through the foil with little or no deflection.

What does this observation show about the structure of gold atoms?

AMost of the atom is empty space BThe gold foil is very thin CAlpha particles have a very high speed DGold atoms have a small positive charge

Question 2

The alpha scattering experiment was first carried out under the direction of Ernest Rutherford at Cambridge's Cavendish Laboratory. Before this experiment, the accepted model was Thomson's “plum pudding” model.

What did the alpha scattering experiment prove about the atom?

APositive charge is spread evenly throughout the atom BThe atom contains electrons embedded in a positive sphere CThe positive charge and most of the mass are concentrated in a small, dense nucleus DAtoms contain equal numbers of protons and neutrons

Question 3

A uranium nucleus is represented as ²³⁵₉₂U.

How many neutrons are in this nucleus?

A92 B143 C235 D327

Question 4

Carbon-12 and carbon-14 are isotopes of carbon. They are both used in scientific research — carbon-14 is used for radiocarbon dating at the British Museum.

In what way do the atoms of carbon-12 and carbon-14 differ?

AThey have different numbers of protons BThey have different numbers of electrons CThey have different chemical properties DThey have different numbers of neutrons

Question 5

Cobalt-60 (⁶⁰₂₇Co) is used in NHS hospitals for cancer radiotherapy.

Which row correctly describes the composition of a cobalt-60 nucleus?

	Protons	Neutrons	Electrons
A	27	33	27
B	33	27	33
C	27	33	0
D	60	27	0

ARow A BRow B CRow C DRow D

Question 6

In the alpha scattering experiment, a very small fraction of the alpha particles bounce back towards the source.

What does this observation tell us?

AThe gold foil is too thick for alpha particles to penetrate BThe nucleus is very small compared to the overall size of the atom CAlpha particles are easily stopped by metal DThe electrons in the atom repel the alpha particles

Question 7

Chlorine has two naturally occurring isotopes: ³⁵₁₇Cl and ³⁷₁₇Cl.

Which statement about these two isotopes is correct?

AThey have different chemical properties because they have different masses BThey have different numbers of protons in their nuclei CThey have the same chemical properties but different masses DThey have the same number of neutrons but different numbers of electrons

Question 8

At the Hinkley Point C nuclear power station in Somerset, uranium-235 is used as fuel. A neutron strikes a uranium-235 nucleus and the nucleus undergoes fission.

What happens during this process?

ATwo small nuclei combine to form a larger nucleus, releasing energy BThe uranium nucleus splits into two smaller nuclei, releasing neutrons and energy CThe uranium nucleus absorbs the neutron and emits gamma radiation only DThe uranium nucleus loses an alpha particle and becomes thorium

Question 9

Nuclear fusion occurs in the core of the Sun. Hydrogen nuclei (protons) fuse together to form helium nuclei.

Why is an extremely high temperature needed for fusion to occur?

ATo melt the hydrogen so the nuclei can mix together BTo break the covalent bonds between hydrogen atoms CTo remove the electrons from the hydrogen atoms DTo give the nuclei enough kinetic energy to overcome the electrostatic repulsion between them

Question 10

Which diagram correctly shows the nuclear model of an atom?

AModel A BModel B CModel C DModel D

Question 11

A physics teacher in the Scottish Highlands measures the background radiation count rate in her classroom. The reading is higher than the UK average.

What is the most likely reason for this?

AThe school is near a mobile phone mast BRadon gas seeps up from the granite rocks beneath the school CThe school is at a higher altitude, closer to the ozone layer DThe school uses nuclear power for its electricity supply

Question 12

A student at an Oxford physics lab tests three radioactive sources using a Geiger-Müller tube. She places different absorbers between each source and the detector.

The table shows her results.

Source	No absorber	Sheet of paper	5 mm aluminium	3 cm lead
P	High count	Background only	Background only	Background only
Q	High count	High count	Background only	Background only
R	High count	High count	High count	Reduced count

Which row correctly identifies the type of radiation from each source?

	Source P	Source Q	Source R
A	gamma	beta	alpha
B	beta	alpha	gamma
C	alpha	beta	gamma
D	alpha	gamma	beta

ARow A BRow B CRow C DRow D

Question 13

Alpha, beta and gamma radiations pass between two parallel charged plates as shown in the diagram.

Which type of radiation shows the greatest deflection?

AAlpha, because it has the largest charge (+2) BBeta, because it has a much smaller mass than alpha CGamma, because it travels at the speed of light DAll three are deflected equally

Question 14

An NHS hospital needs to sterilise surgical instruments by exposing them to radiation.

Which property makes gamma radiation the most suitable choice?

AIt has the highest ionising power BIt can be stopped by a thin sheet of aluminium CIt has high penetrating power, passing through packaging to reach all surfaces DIt has a very short range in air, so it stays contained

Question 15

A radioactive source emits radiation that is completely absorbed by a few centimetres of air. The radiation has no penetrating power beyond this distance.

What type of radiation does the source emit?

AAlpha BBeta CGamma DX-rays

Question 16

In a magnetic field, alpha particles and beta particles curve in opposite directions.

Why do they curve in opposite directions?

AThey have different masses BThey travel at different speeds CThey have different penetrating powers DThey have opposite charges

Question 17

Which row correctly compares the three types of nuclear radiation?

	Ionising power	Penetrating power	Charge
A	alpha > beta > gamma	alpha > beta > gamma	alpha +2, beta −1, gamma 0
B	gamma > beta > alpha	gamma > beta > alpha	alpha +2, beta −1, gamma 0
C	alpha > beta > gamma	gamma > beta > alpha	alpha +2, beta −1, gamma 0
D	alpha > beta > gamma	gamma > beta > alpha	alpha +2, beta +1, gamma 0

ARow A BRow B CRow C DRow D

Question 18

Radium-226 (²²⁶₈₈Ra) undergoes alpha decay.

Which equation correctly represents this decay?

A²²⁶₈₈Ra → ⁴₂He + ²²²₈₄Po B²²⁶₈₈Ra → ⁴₂He + ²²⁴₈₆Rn C²²⁶₈₈Ra → ⁴₂He + ²²²₈₆Rn D²²⁶₈₈Ra → ⁴₂He + ²²²₈₈Rn

Question 19

A nucleus undergoes beta (β⁻) decay.

What changes occur in the nucleus?

AMass number decreases by 4, atomic number decreases by 2 BMass number stays the same, atomic number increases by 1 CMass number decreases by 1, atomic number increases by 1 DMass number stays the same, atomic number decreases by 1

Question 20

Cobalt-60 (⁶⁰₂₇Co) is used in NHS cancer treatment. It decays by beta emission.

What is the daughter nucleus produced?

A⁶⁰₂₈Ni (nickel-60) B⁶⁰₂₆Fe (iron-60) C⁵⁶₂₅Mn (manganese-56) D⁵⁹₂₇Co (cobalt-59)

Question 21

Which instrument can be used to measure the count rate of radiation from a radioactive source?

AA photographic film badge BA Geiger-Müller tube connected to a ratemeter CA cloud chamber DA gold-leaf electroscope

Question 22

A charged gold-leaf electroscope has its leaf raised. A radioactive source is brought near the cap of the electroscope and the leaf gradually falls.

What can be concluded from this observation?

AThe source emits only alpha radiation BThe source emits only beta radiation CThe source emits only gamma radiation DThe source emits ionising radiation

Question 23

A radioactive sample has an initial activity of 800 Bq. After 3 half-lives, what is the activity of the sample?

A267 Bq B200 Bq C100 Bq D400 Bq

Question 24

In a school laboratory, the background count rate is 20 counts per minute. A radioactive source gives an initial reading of 180 counts per minute on the detector. After 2 hours, the reading is 60 counts per minute.

What is the corrected count rate from the source after 2 hours?

A60 counts/min B40 counts/min C80 counts/min D20 counts/min

Question 25

The graph shows how the total count rate (including background) from a radioactive source changes with time. The background count rate is 30 counts per minute.

What is the half-life of this source?

A5 minutes B10 minutes C15 minutes D20 minutes

Question 26

Technetium-99m has a half-life of 6 hours. A patient at an NHS hospital is injected with technetium-99m at 9:00 am. The initial activity is 800 MBq.

What is the activity at 9:00 pm on the same day?

A400 MBq B100 MBq C200 MBq D67 MBq

Question 27

Iodine-131 has a half-life of 8 days. A hospital starts with a sample of 64 mg of iodine-131.

How many days will it take until only 2 mg of the original iodine-131 remains?

A16 days B24 days C32 days D40 days

Question 28

The count rate from a radioactive source drops from 400 counts per minute to 50 counts per minute. (Ignore background radiation.)

How many half-lives have passed?

A2 B3 C4 D8

Question 29

A student is calculating the half-life of a radioactive source from experimental data.

Why must the background count rate be subtracted from the measured count rate before the half-life can be determined?

AThe background count rate makes the source appear more dangerous than it is BThe background count rate is always zero and can be ignored CThe background count adds a constant value that is not from the source and would give an incorrect half-life DThe background radiation has its own half-life that must be accounted for

Question 30

Nuclear waste stored at Sellafield contains a radioactive isotope with a half-life of 30 years.

How long will it take for the activity to fall to 1/8 of its original value?

A3.75 years B60 years C90 years D240 years

Question 31

Carbon-14 has a half-life of 5730 years. An ancient wooden bowl examined by the British Museum is found to contain 1/4 of the original carbon-14 content.

How old is the bowl?

A5 730 years B11 460 years C17 190 years D22 920 years

Question 32

The graph shows how the corrected count rate of a radioactive source changes with time.

What is the half-life of this source?

A1 hour B2 hours C4 hours D8 hours

Question 33

A radioactive source gives a detector reading of 1200 Bq. The background radiation is 40 Bq. After 4 half-lives, what reading will the detector show?

A75 Bq B72.5 Bq C40 Bq D112.5 Bq

Question 34

A UK smoke detector contains americium-241, which emits alpha radiation. A small gap inside the detector is filled with air that is ionised by the alpha particles.

Why is an alpha emitter used instead of a beta or gamma emitter?

AAlpha is strongly ionising and has a short range, so it ionises the air inside the detector but does not penetrate the casing BAlpha has high penetrating power, so it can pass through smoke particles CAlpha radiation is the least ionising, so it is the safest to use in homes DAlpha particles are uncharged, so they do not affect the electrical circuit

Question 35

Food irradiation is used at some UK food processing facilities to kill bacteria and extend shelf life. Cobalt-60 (a gamma emitter) is used for this purpose.

Why is gamma radiation used rather than alpha radiation?

AGamma makes the food radioactive, which helps kill bacteria inside BAlpha radiation would make the food too hot to eat CGamma can penetrate the packaging to reach the food inside, and does not make the food radioactive DAlpha radiation would destroy the packaging completely

Question 36

A paper manufacturing factory uses a radioactive source and detector to monitor the thickness of paper as it is produced. If the paper is too thick or too thin, the detector reading changes and the rollers are adjusted automatically.

Which type of source and half-life should be used?

AAlpha source with a long half-life BBeta source with a long half-life CGamma source with a short half-life DGamma source with a long half-life

Question 37

A radiographer at an NHS hospital handles radioactive sources regularly.

Which of the following is NOT a correct safety precaution?

AHandle sources with long tongs to increase the distance from the body BStore sources in a lead-lined container when not in use CHold the source close to the body to reduce the time of exposure DWear a film badge to monitor total radiation dose received

Question 38

Technetium-99m (half-life 6 hours, gamma emitter) is preferred over cobalt-60 (half-life 5.3 years, beta and gamma emitter) as a medical tracer injected into a patient.

Why is technetium-99m more suitable?

ATechnetium-99m has a longer half-life so gives more time for scanning BTechnetium-99m has a short half-life and emits gamma only, so it does not remain in the body for long and can be detected outside the body CTechnetium-99m is an alpha emitter, which is better at killing cancer cells DCobalt-60 cannot be produced in hospitals

Question 39

Radioactive waste from Sellafield is classified by activity level. High-level waste remains dangerously radioactive for thousands of years.

Which storage method is appropriate for high-level waste?

ADiluting it with water and releasing it into the sea BStoring it in steel drums on the surface at the power station CMixing it into glass (vitrification) and burying it deep underground in stable geological formations DBurning it at very high temperatures to destroy the radioactivity

Question 40

At CERN, scientists created new elements by firing beams of iron nuclei at lead targets. The nuclear equation for one such reaction is:

²⁰⁸₈₂Pb + ⁵⁸₂₆Fe → ²⁶⁵₁₀₈Hs + x ¹₀n

How many neutrons (x) are produced in this reaction?

A1 B2 C3 D4

Paper 2 — Multiple Choice

Section A: Atomic Structure

Section B: Radiation Types & Properties

Section C: Half-life Calculations

Section D: Applications & Safety