IGCSE Physics 0625 — Topic 5: Nuclear Physics

Question 1

What is the approximate diameter of an atom?

A10⁻¹⁰ m B10⁻¹⁵ m C10⁻⁵ m D10⁻² m

Question 2

An atom has 11 protons, 12 neutrons and 11 electrons. What is the nucleon number (mass number) of this atom?

A11 B12 C23 D34

Question 3

Which particle in an atom has a negative charge?

Aproton Bneutron Celectron Dnucleus

Question 4

Two atoms are isotopes of the same element. Which statement about them must be correct?

AThey have the same number of protons but different numbers of neutrons. BThey have the same number of neutrons but different numbers of protons. CThey have the same nucleon number but different proton numbers. DThey have different numbers of electrons and different numbers of protons.

Question 5

In the Rutherford alpha-particle scattering experiment, most alpha particles passed straight through the gold foil. What does this observation show about the atom?

AThe atom is mostly empty space. BThe nucleus is negatively charged. CThe electrons are inside the nucleus. DThe atom has no internal structure.

Question 6

The nuclide notation for an atom is written as ¹⁴₆C. How many neutrons does this atom contain?

A6 B8 C14 D20

Question 7

Nuclear fission is the process in which:

Atwo small nuclei combine to form a larger nucleus Ba large nucleus splits into two smaller nuclei, releasing energy Can electron is emitted from the nucleus Da neutron is absorbed by an electron

Question 8

Nuclear fusion occurs naturally in:

Anuclear power stations Bstars Cradioactive rocks Dsmoke detectors

Question 9

In the alpha-particle scattering experiment, a small number of alpha particles bounced back towards the source. What does this observation indicate about the nucleus?

AThe nucleus is very small and has a large positive charge. BThe nucleus is spread evenly throughout the atom. CThe nucleus is negatively charged. DThe nucleus contains only neutrons.

Question 10

An atom of lithium is represented as ⁷₃Li. Which row correctly shows the number of each particle in this atom?

A3 protons, 4 neutrons, 3 electrons B7 protons, 3 neutrons, 7 electrons C3 protons, 7 neutrons, 3 electrons D4 protons, 3 neutrons, 4 electrons

Question 11

A Geiger-Müller tube records 40 counts per minute with no radioactive source nearby. A radioactive source is then placed near the tube and the count rate rises to 340 counts per minute. What is the corrected count rate from the source?

A340 counts per minute B300 counts per minute C280 counts per minute D380 counts per minute

Question 12

Which of the following is NOT a source of background radiation?

Acosmic rays from space Bradon gas from rocks Cvisible light from the Sun Dradioactive isotopes in food

Question 13

An alpha particle is the same as:

Aa high-energy electron Ba helium nucleus (2 protons and 2 neutrons) Can electromagnetic wave Da single proton

Question 14

Which type of radiation has the greatest ionising power?

Aalpha Bbeta Cgamma DAll three have the same ionising power.

Question 15

Which type of radiation can pass through several centimetres of lead?

Aalpha only Bbeta only Cgamma only Dalpha and beta

Question 16

A beta particle is:

Aa helium nucleus emitted from the nucleus Ba high-speed electron emitted from the nucleus Can electromagnetic wave emitted from the nucleus Dan electron from the outer shell of the atom

Question 17

A radioactive source emits radiation that is stopped by a thin sheet of paper but not by air. Which type of radiation is this?

Aalpha Bbeta Cgamma DX-rays

Question 18

Radioactive decay is described as random and spontaneous. What does ‘spontaneous’ mean in this context?

AIt cannot be predicted which nucleus will decay next. BIt is not caused by any external conditions and cannot be controlled. CIt happens at a constant rate. DIt can be speeded up by heating the sample.

Question 19

When a nucleus emits an alpha particle, what happens to the proton number (Z) and the nucleon number (A)?

AZ decreases by 2 and A decreases by 4 BZ increases by 2 and A increases by 4 CZ decreases by 1 and A stays the same DZ decreases by 4 and A decreases by 2

Question 20

When a nucleus undergoes beta decay, a neutron in the nucleus changes into:

Aa proton and an electron Btwo protons Ca proton and a neutron Dan alpha particle

Question 21

²²⁶₈₈Ra decays by emitting an alpha particle. What is the nuclide notation of the daughter nucleus?

A²²²₈₆Rn B²²⁴₈₆Rn C²²⁶₈₉Ac D²³⁰₉₀Th

Question 22

¹⁴₆C undergoes beta decay. What is the daughter nucleus?

A¹⁴₇N B¹⁰₄Be C¹⁴₅B D¹²₆C

Question 23

Alpha, beta and gamma radiations are passed through an electric field. Which statement is correct?

AAlpha and beta are deflected in the same direction; gamma is not deflected. BAlpha and beta are deflected in opposite directions; gamma is not deflected. COnly gamma is deflected. DNone of the three types is deflected.

Question 24

Which property of gamma radiation makes it suitable for sterilising medical equipment?

AIt is strongly ionising. BIt is highly penetrating and can kill bacteria inside sealed packaging. CIt has a positive charge. DIt is stopped by a few centimetres of aluminium.

Question 25

A Geiger-Müller tube detects radiation from a source. The source is moved further from the tube. Which statement about the count rate is correct?

AThe count rate will decrease but never reach zero because of background radiation. BThe count rate will remain constant. CThe count rate will increase. DThe count rate will drop to exactly zero.

Question 26

What is the definition of half-life?

AThe time taken for the count rate from a sample to fall to half its initial value BThe time taken for all the atoms in a sample to decay CThe time taken for the sample to lose half its mass DThe time taken for a radioactive atom to emit one particle

Question 27

A radioactive sample has an initial activity of 800 Bq. After 30 minutes, the activity has fallen to 100 Bq. What is the half-life of the sample?

A5 minutes B10 minutes C15 minutes D30 minutes

Question 28

A source has a half-life of 6 hours. The initial corrected count rate is 1200 counts per minute. What will the corrected count rate be after 18 hours?

A600 counts per minute B300 counts per minute C150 counts per minute D75 counts per minute

Question 29

A radioactive sample initially contains 4800 undecayed atoms. After 3 half-lives, how many undecayed atoms remain?

A1600 B1200 C600 D400

Question 30

The background count rate is 20 counts per minute. A radioactive source gives a total count rate of 820 counts per minute at time zero. After 4 hours the total count rate is 120 counts per minute. What is the half-life of the source?

A30 minutes B1 hour C80 minutes D2 hours

Question 31

An isotope used in a smoke detector must have a long half-life. Which is the best reason for this?

ASo that the source emits a high level of radiation at first. BSo that the source remains active and effective for many years without frequent replacement. CSo that the source can be disposed of easily. DSo that the radiation is more penetrating.

Question 32

A factory uses a radioactive source and detector to monitor the thickness of metal sheets. The source should emit:

Aalpha particles, because they are the most ionising Bbeta particles, because they are partially absorbed by metal Cgamma rays, because they pass through all thicknesses of metal Dalpha particles, because they are not deflected by magnetic fields

Question 33

The table shows the corrected count rate of a radioactive sample over time.

Time (min): 0 10 20 30 40
Count rate (cpm): 640 320 160 80 40

What is the half-life of the sample?

A5 minutes B10 minutes C20 minutes D40 minutes

Question 34

A medical tracer injected into a patient should have a half-life that is:

Aa few seconds, so the patient receives the minimum possible dose Blong enough to complete the medical test but short enough to limit patient exposure Cmany thousands of years to ensure the tracer lasts a long time Dexactly one second for all medical procedures

Question 35

A radioactive isotope has a half-life of 8 days. A sample initially has an activity of 6400 Bq. How many days will it take for the activity to fall to 200 Bq?

A24 days B32 days C40 days D48 days

Question 36

Which statement correctly describes a biological effect of ionising radiation on living cells?

AIonising radiation can damage DNA in cells, which may cause mutations or cancer. BIonising radiation strengthens cells and makes them more resistant to disease. CIonising radiation has no effect on biological cells. DIonising radiation only damages plant cells, not animal cells.

Question 37

A scientist is working with a gamma source. Which of the following is NOT a recommended safety precaution?

AKeep the source at arm’s length and use tongs to handle it. BPoint the source away from the body. CHold the source close to the eyes to observe it more carefully. DStore the source in a lead-lined container when not in use.

Question 38

The three key safety principles when working with radioactive sources are to minimise exposure time, maximise distance from the source, and:

Aheat the source to reduce its activity Buse appropriate shielding between the source and the person Cdissolve the source in water Dpaint the source with a bright colour for visibility

Question 39

Gamma rays are used to treat cancerous tumours. Why is the gamma beam rotated around the patient during treatment?

ATo ensure only the tumour receives a high total dose, while surrounding healthy tissue receives a lower dose from each angle. BTo make the gamma rays more ionising. CTo increase the speed of the gamma rays. DTo convert the gamma rays into alpha particles for greater effect.

Question 40

Food can be preserved by exposing it to gamma radiation. Which statement best explains why gamma radiation is used rather than alpha or beta radiation for this purpose?

AGamma rays penetrate deep into the food to kill bacteria throughout, without making the food radioactive. BGamma rays make the food taste better. CGamma rays are positively charged so they attract bacteria. DAlpha particles would be better but are too expensive to produce.

Paper 2 — Multiple Choice

Section A — Atomic Structure

Section B — Radiation Detection, Types & Decay

Section C — Half-life

Section D — Safety & Applications