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1

A freshly prepared sample contains 4.0 μg of iodine-131. After 24 days, 0.5 μg of iodine-131 remain. The best estimate of the half-life of iodine-131 is
A.    8 days.
B.    12 days.
C.    24 days.
D.    72 days.

A.    8 days.

 

2

Which nucleons in a nucleus are involved in the Coulomb interaction and the strong short-range nuclear interaction?


              Coulomb interaction              Strong short-range interaction
A.                 protons                                           protons, neutrons
B.                 protons                                              neutrons
C.                protons                                                 protons
D.           protons, neutrons                                    neutrons

A. Coulomb interaction involves protons while strong short-range interaction involves both protons and neutrons

3

Two samples of radioactive substances X and Y have the same initial activity. The half-life of X is T and the half-life of Y is 3T. After a time of 3T the ratio
                                activity of substance X/activity of substance Y  is
A.    8.
B.    4.
C.     1/4
D.     1/8

 

C. 1/4

4

The nuclear equation below is an example of the transmutation of mercury into gold.

The particle X is a
A.    gamma-ray photon.
B.    helium nucleus.
C.    proton.
D.    neutron.

 

 

B.    helium nucleus.

5

Define binding energy of a nucleus.

the (minimum) energy required to completely separate the
nucleons of a nucleus / the energy released when a nucleus
is assembled;

6

Stable nuclei with a mass number greater than about 20, contain more neutrons than protons. By reference to the properties of the nuclear force and of the electrostatic force, suggest an explanation for this observation.

the electric force is repulsive/tends to split the nucleus;
the electric force acts on protons, the strong nuclear force acts on nucleons;
the nuclear force is attractive/binds the nucleons;
but the electric force is long range whereas the nuclear force is short range;
so adding more neutrons (compared to protons) contributes to
binding and does not add to tendency to split the nucleus / a
proton repels every other proton (in the nucleus) so extra neutrons
are needed for binding;

7

Define the term unified atomic mass unit.

 (1/2) the mass of an atom of carbon–12/12C

8

State what is meant by the term isotopes.

 

(nuclei of same element with) same proton number,
different number of neutrons / OWTTE;

9

Define the term radioactive half-life.

the time for the activity of a sample to reduce by half / time
for the number of the radioactive nuclei to halve from original value;

10

State what is meant by the photoelectric effect.

 

ejection of electron from metal surface following absorption of
em radiation/photon;

11

Define decay constant.

 

probability that a nucleus decays in unit time;

12

Outline how the half-life of a sample of nitrogen-13 can be measured in a laboratory.

activity/count rate measured at regular time intervals/for at least
three half-lives;
plot graph activity/count rate versus time;
detail of determination of half-life from graph;

13

Nuclei with a Z number greater than about 20 and which are stable against radioactive decay have

A. equal numbers of neutrons and protons.

B. more neutrons than protons.

C. fewer neutrons than protons.

D. no neutrons.

B. more neutrons than protons

14

What type of single radioactive decay process does not change the value of Z, the value of N or the value of A?

A. Only beta decay

B. Only alpha decay

C. Only gamma decay

D. Both beta and gamma decay

C. Only gamma decay

15

Two radioactive sources X and Y have the same initial activity. X has a half life of 2 hours and Y a half life of 1 hour. What is the ratio of the activities of X to Y after 4 hours?

A. 2 : 1

B. 4 : 1

C. 8 : 1

D. 16 : 1

B. 4 : 1 

16

Cathode rays consist of

A. electrons.

B. photons.

C. helium nuclei.

D. neutrons

A. electrons.

17

Thermionic emission is

A. the emission of radiation from a hot object.

B. the emission of particles from a radioactive substance.

C. the ejection of electrons from a surface by incident radiation.

D. the emission of electrons from a hot object.

D. the emission of electrons from a hot object.

18

Nuclide X decays with a half-life of 20 days to stable nuclide Y. At a particular time, a sample consists of nuclides X and Y in the ratio 1 : 1. How much time will elapse before the ratio becomes 1 : 3?

A. 20 days

B. 40 days

C. 60 days

D. 80 days

A. 20 days 

19

All the isotopes of an element have nuclei with the same

A. mass.

B. number of nucleons.

C. number of protons.

D. number of neutrons.

C. number of protons. 

20

A sample consists of a mixture of two radioactive nuclides X and Y, each of which decay to stable products. The half-life of X is about a day, while that of Y is about a week. If the activities due to X and Y are equal at a particular time, then a few days later the activity of the sample will be

A. due to nuclides X and Y equally.

B. entirely due to nuclide Y.

C. predominantly due to nuclide X.

D. predominantly due to nuclide Y

D. predominantly due to nuclide Y

21

Which of the following best describes the principle of operation of a Geiger-Muller tube used to detect alpha particles?

A. The electric charge of the alpha particle is recorded as an electric pulse as it strikes the inside of the tube.

B. The alpha particle ionizes gas atoms or molecules along its path, the ions and electrons are separated and are detected as an electric pulse.

C. The alpha particle causes a flash of light in the tube, and each flash is counted electronically.

D. The alpha particle causes a nuclear reaction with a gas atom in the tube, and the reaction products produce an electric pulse.

B. The alpha particle ionizes gas atoms or molecules along its path, the ions and electrons are separated and are detected as an electric pulse. 

22

Which one of the following correctly gives the number of electrons, protons and neutrons in a neutral atom of the nuclide?

D. 29 electrons, 29 protons, 36 neutrons

23

In the Geiger-Marsden experiment, α particles are scattered by gold nuclei. The experimental results indicate that most particles are α

A. scattered only at small angles.

B. scattered only at large angles.

C. absorbed in the target.

D. scattered back along the original direction.

A. scattered only at small angles. 

24

A sample of radioactive carbon-14 decays into a stable isotope of nitrogen. As the carbon-14 decays, the rate at which the amount of nitrogen is produced

A. decreases linearly with time.

B. increases linearly with time.

C. decreases exponentially with time.

D. increases exponentially with time.

C. decreases exponentially with time. 

25

The unified mass unit is defined as

A. the mass of one neutral atom of . 12 6C

B. 1/12 of the mass of one neutral atom of 12 6C

C. 1/6 of the mass of one neutral atom of . 12 6C

D. the mass of the nucleus of 12 6 C.

B. 1/12 of the mass of one neutral atom of 12 6

26

Which one of the following provides direct evidence for the existence of discrete energy levels in an atom?

A. The continuous spectrum of the light emitted by a white-hot metal.

B. The line emission spectrum of a gas at low pressure.

C. The emission of gamma radiation from radioactive atoms.

D. The ionization of gas atoms when bombarded by alpha particles.

B. The line emission spectrum of a gas at low pressure. 

27

A sample of material initially contains atoms of only one radioactive isotope. Which one of the following quantities is reduced to one half of its initial value during a time equal to the half-life of the radioactive isotope?

A. Total mass of the sample

B. Total number of atoms in the sample

C. Total number of nuclei in the sample

D. Activity of the radioactive isotope in the sample

D. Activity of the radioactive isotope in the sample

28

In a fission chain reaction,

A. energy from one fission reaction causes further fission reactions.

B. nuclei produced in one fission reaction cause further fission reactions.

C. neutrons from one fission reaction cause further fission reactions.

D. gamma radiation produced in one fission reaction causes further fission reactions.

C. neutrons from one fission reaction cause further fission reactions.

29

Which one of the following correctly identifies the atomic (proton) number and mass (nucleon) number of a nucleus that has neutrons n and protons p?

B. protons represented by p, mass number represented by p+n

30

In a laboratory when aluminium nuclei are bombarded with "a-particles, the following reaction may take place.

This reaction is an example of

A. nuclear fission.

B. nuclear fusion.

C. natural radioactive decay.

D. artificial transmutation.

D. artificial transmutation.