OBJECTIVE QUESTIONS

CHAPTER 10( RADIOACTIVE) PAPER 11 The diagram shows the path of radioactive rays, S and T.

Ray S

Ray T

Paper Aluminium foil Lead

Which of the following shows the type of ray S and ray T?

Ray S

Ray T

A

(

B

C (

D (2 The table shows the half-lives of radioisotopes J, K, L and M.Radioisotope Half-life

J

K

L

M 8 days

56 days

5.27 years

6 hours

Which of the radioisotopes is most suitable as a tracer in the human body?

A

J

B

K

C

L

D

M

3 Cobalt-60 destroys cancer cells because it

Ahas a long half-life

Bhas no side effect

Cradiates gamma rays

Ddecays spontaneously

20041 Which of the following pairs of atoms can act as an impurity to produce an n-type semiconductor when doped into a pure semiconductor?

ABoron and phosphorus

BArsenic and antimony

CIndium and gallium

DAntimony and gallium

2 The graph shows the decay curve of a radioactive material.

If the initial activity of the radioactive material is 800 counts per minute, what is

the activity after 1 hour?

A400

B200

C100

D50

E253 The diagram shows a series of radioactive decays for the nucleus of uranium-238 to that of radium-226.

Nucleon number (A)

238 U 234 U 230 226 222Proton

87 88 89 90 91 92 number (Z)What is the number of alpha particles and beta particles emitted during this process?

The number of alpha particles The number of beta particlesA

2

3

B

3

2

C

4

1

D

1

14 Which of the following has a similar characteristic to (-particles?AProton

BElectron

CHelium nucleus

DElectromagnetic wave

2005

1 The following equation represents the decay of a uranium nucleus.

What are the values of x and y?

X

y

A

0

1

B

1

1

C

1

2

D

2

2

2 What is the radioisotope that can be used to determine the age of a fossil?

A

Radon-222

B

Uranium-238

C

Carbon-14

D

Iodine-131

3 Which of the following statements is a characteristic of gamma radiation?A

It has a positive charge

B

It is an electromagnetic wave

C

It has a higher ionizing power than alpha radiation

D

It has a lower penetrating power than beta radiation

2006

1 The diagram shows three types of radioactive rays, X, Y and Z, directed towards a sheet of paper, a sheet of aluminium and a sheet of lead.

X

Y

Z Paper

Aluminium

Lead

Which of the following rays are represented by X, Y and Z?

X

Y

Z

A

Alpha

Gamma

Beta

B

Beta

Alpha

Gamma

C

Gamma

Alpha

Beta

D

Gamma

Beta

Alpha

2 The initial mass of a radioactive element is 10 g and its half-life is 6 days.

Which of the following statements about the mass of the radioactive element is true?

A

6 days earlier, the mass is 20 g

B

12 days earlier, the mass is 80 g

C

6 days later, the mass is 2.5 g

D

12 days later, the mass is 5.0 g

3 Which statement is true about the use of radioactive substance?

A

To determine the sex of a foetus

B

To determine the contents in the baggage of the air plane passengers

C

To detect leakage in underground pipes

D

To identify counterfeit bank-notes2007

1A negatively charged particle moves towards a nucleus of an atom.

Which of the following diagram shows the correct path of the particle ?

2.Table 1 shows the half-lives of four types of liquid isotopes which radiate - particles.

Which of the following isotopes is suitable to detect blood clotting ?

A. P

B. Q

C. R

D. S

3.In the fission reaction for an atom of uranium-235, the energy produced is 2.9 x 10-11J.

What is the total loss of mass in the reaction ?

A. 3.22 x 10-28 kg

B. 9.67 x 10-20 kg

C. 2.61 x 106 kg

D. 1.03 x 1019 kgPAPER 22003 (SECTION C)

1 As a researcher, you are assigned to investigate the characteristics of a certain radioactive isotope that could be used to detect the thickness of paper in a paper factory.(a)What does the term isotope mean?

[ 1 mark]

(b)The table below shows the characteristics of five isotopes.

IsotopeState of matterEmmited radiationHalf-lifePenetrating power

Strontium-90

Cobalt-60

Xenon-133

Water containing H-3

Polonium-210 SolidSolid

Gas

Liquid

SolidBeta

Gamma

Beta

Beta

Alpha28 years5 years

5 days

12 years

140 days

MediumHigh

High

Medium

Low

Based on the table above;

(i) Explain the suitable characteristics of the isotopes so that it can be used to measure the thickness of paper in a paper industry.

(ii) Select the most suitable isotope to be used in detecting the thickness of paper in the factory and give your reasons.[ 10 marks]

(c) Suggest briefly the arrangement of the paper thickness detector apparatus and state how radioactivity is used to detect the thickness of the paper.

[ 3 marks]

(d) Sketch a graph of activity against time to illustrate how radioactive materials decay. Use your graph to explain how the half-life is determined.

[ 4 marks]

(e) The half-life of cobalt-60 is 5 years.

Calculate the time taken for the activity of this isotope to decay to 12.5% of its initial value.

[ 2 marks]2004 (SECTION B)

1Production of nuclear energy and detecting the volume of a material are two examples of the use of radioactive materials in industry.

Table 2.1 shows an equation of a reaction and total atomic mass before and after a nuclear fission.

Nuclear fission

Equation + + + 2 +

Total atomic mass240.06082 a.m.u 239.85830 a.m.u

Before reaction

After reactionTABLE 2.1Table 2.2 shows an equation of a reaction and total atomic mass before and after a nuclear fusion.Equation + + +

Total atomic

mass 5.03013 a.m.u 5.01043 a.m.u

Nuclear fusion Before reaction

After reaction

TABLE 2.2

(a)(i)What is meant by a nuclear fission?

[ 1 mark]

(ii)Using only the information given in Table 2.1 and 2.2, compare nuclear fission and nuclear fusion. Hence state the relationship between mass and energy evolved.

[ 5 marks]

(b)Nuclear fission produces a chain reaction.

Describe how the chain reaction happens in a nuclear fission of an atom uranium.

[ 4 marks](c) A paint-producing factory wants to develop a volume control system which can ensure the quantity of paint in every tin is within a specific range. The tins of paint are transported on a conveyor belt as shown in Figure 2.1. If the volume of the paint is less or more than the specific range of volume, the tin will be separated automatically.

FIGURE 2.1

Using your knowledge on radioactivity and Figure 2.1, explain;

(i)the radioactivity material and equipment required to develop the volume

control system,

(ii)how the equipment is assembled,

(iii)how the system works.

[10 marks]2005 (SECTION A)

1 (a)A grazing pasture was polluted with radioactive waste from a nuclear reactor. A

researcher carried out a study on the radioactive content in the milk collected from the cows in that area. He discovered the radioactive content in every litre of the milk was 1600 counts per minute.

The researcher continued to measure the radioactivity in the milk from that area in 10 day intervals.

The results of the study are shown in Table 7.1.

Time/day010203040

Radioactivity/counts per minute160060024010040

TABLE 7.1

(i)On the graph paper below, draw a graph of radioactivity against time.

[2 marks]

(ii)Using the graph in (a)(i), determine the half-life of the radioactive material in the milk.

Show on the graph how you determined the half-life.

The half-life is . days.

[2 marks](iii)Milk is safe to drink if the radioactivity in every litre of the milk is not more than 50 counts per minute.

Using the half-life in (a)(ii), calculate the time when the milk from this area becomes safe to drink.

[2 marks]

(b)In a nuclear reactor, radium-226 decays to become radon-222 by releasing one alpha particle. This reaction experiences a mass defect.

(i)The number 226 for radium is called its . number.

[1 mark]

(ii)Complete the equation of the reaction by writing the appropriate number in the

boxes provided.

++

[1 mark]

(iii) The nuclear reaction of one nucleus of radium-226 experiences a mass defect of 8.6818 ( 10 kg.

Calculate the energy released in the nuclear reaction.

[ 2 mark]

The velocity of light is 3 ( 10 m s .2006 (SECTION C)

1Radioactive material has some uses in the medical field such as in the investigation of internal organs and in the sterilization of equipments.

(a)A doctor conducts an investigation on a patients kidney by injecting iodine-131

radioisotope, that has a half-life of 8 days, into the blood circulation.

A normal kidney can expel radioisotope in 20 minutes.

The presence of radioisotope in the left and right kidneys is shown in the graphs as in

Diagram 12.1.

(i)What is meant by half-life?

[1 mark]

(ii)Based on the graphs in Diagram 12.1, which kidney is not functioning properly?

Give one reason.

[2 marks]

(iii)The initial iodine-131 activity is 1600 counts per second.

Calculate the time taken for the iodine-131 activity to decrease to 100 counts per

second.

[2 marks]

(b)Medical equipment is sterilized by radiation from a radioactive source.

You are assigned to study the characteristics of some radioisotopes that are suitable

for use in sterilization of medical equipments.

Table 12 shows the characteristics of five radioisotopes.

Radioisotope

Characteristics of isotope

State of Types of ray Half-life matter

Strontium-90Cobalt-60

Xenon-133

Iodine-131

Polonium-210 Solid Beta 28 years

Solid Gamma 5 years

Gas Beta 5 days

Liquid Gamma 8 days

Solid Alpha 140 days

(i)Explain the suitability of the characteristics of the radioisotope to be used in

the sterilization of medical equipment.

[6 marks]

(ii)Determine the most suitable radioisotope to be used and give one reason for

your choice.

[2 marks]

(c) Gamma rays can produce an effect on photographic film.

Explain whether gamma rays is suitable to be used in taking photographs of an organ

in humans.

[2 marks]

(d)Beryllium-11 isotope emits two rays. The isotope is placed in front of a magnetic field

and the radioactive radiation path is shown in Diagram 12.2.

(i)Name both rays that are emitted by the isotope.

[2 marks]

(ii)Explain why the rays follow the path shown in Diagram 12.2.

[2 marks]

2007 (No Question)QUESTIONActivity/counts per minute

800

400

0

Time/minutes

15

0

Th

Th

Ra

Pa

+

+

y

He

4

2

e

x

0

-1

Th

230

90

U

238

92

Characteristics of isotope

Energy

n

1

0

Sr

93

38

Ba

145

56

n

1

0

Pu

239

94

Energy

n

1

0

He

4

2

H

2

1

3

1

H

Tin containing paint

Conveyor belt

Ra

226

88

Energy

He

2

Rn

222

-30

8

-1

DIAGRAM 12.1

Right Kidney

Left Kidney

Activity

Activity

TABLE 12

+

Radioactive source

_

DIAGRAM 12.2

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