MS.RAJA ELGADY/RADIOACTIVITY PAPER 31- Fig. 9.1 shows an experiment carried out in a vacuum to investigate the deflectionof

-particles and γ-rays in a magnetic field.

ForExaminer’s

Use

N

magnet

radioactive sourceemitting _-particles

and a-rays

S

lead cylinderwith small hole thin beam of

_-particles anda-rays

Fig. 9.1

(a) Complete the table to describe the deflection, if any, of the α-particles and the γ-rays inthe magnetic field shown. Place one tick in each column.

possible deflection α-particles γ-rays

no deflection

towards N pole of magnet

towards S pole of magnet

out of paper

into paper[3]

(b) The experiment of Fig. 9.1 was carried out in a vacuum.

State the effect of carrying out the experiment in air.

..................................................................................................................................... .....

............................................................................................................................ ..............

............................................................................................................................. ........ [2]

(c) State and explain the purpose of the lead cylinder.

..........................................................................................................................................

............................................................................................................................. .............

..................................................................................................................................... [2]

[Total: 7]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 32- (a) Chlorine has two isotopes, one of nucleon number 35 and one of nucleon number 37.

The proton number of chlorine is 17.

Table 11.1 refers to neutral atoms of chlorine.

Complete Table 11.1.

ForExaminer’s

Use

nucleon number 35 nucleon number 37

number of protons

number of neutrons

number of electrons

Table 11.1[3]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 3(b) Some isotopes are radioactive.

State the three types of radiation that may be emitted from radioactive isotopes.

1. .......................................................

2. .......................................................

3. ....................................................... [1]

(c) (i) State one practical use of a radioactive isotope.

..................................................................................................................................

............................................................................................................................ [1]

(ii) Outline how it is used.

............................................................................................................................... ...

............................................................................................................................. .....

............................................................................................................................. .....

...................................................................................................................... ............

............................................................................................................................ [1] [Total: 6]

3- Emissions from a radioactive source pass through a hole in a lead screen and into a magneticfield, as shown in Fig. 10.1.

radioactivesource

A magnetic fieldinto paper

B

leadscreen

C

3 cm

Fig. 10.1

Radiation detectors are placed at A, B and C. They give the following readings:

MS.RAJA ELGADY/RADIOACTIVITY PAPER 3A B C

32 counts /min 543 counts /min 396 counts /min

The radioactive source is then completely removed, and the readings become:

A B C

33 counts /min 30 counts /min 31 counts /min

(a) Explain why there are still counts being recorded at A, B and C, even when the radioactivesource has been removed, and give the reason for them being slightly different.

............................................................................................................................. ......................

.................................................................................................................................. .................

................................................................................................................ ...................................

............................................................................................................................. ................ [2]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 3(b) From the data given, deduce the type of emission being detected, if any, at A, at B and at C

when the radiation source is present.

State the reasons for your answers.

detector at A .............................................................................................................................

........................................................................................................................................... ........

......................................................................................................................... .................... [2]

detector at B .............................................................................................................................

........................................................................................ ...........................................................

............................................................................................................................. ................ [3]

detector at C .............................................................................................................................

............................................................................................................................. ......................

.......................................................................................................................................... ... [3]

[Total: 10]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 34- Fig. 11.1 shows the paths of three α-particles moving towards a thin gold foil. Examiner’s

Use

MS.RAJA ELGADY/RADIOACTIVITY PAPER 34- Fig. 11.1 shows the paths of three α-particles moving towards a thin gold foil.

MS.RAJA ELGADY/RADIOACTIVITY PAPER 3goldfoil

A

B

C

Fig.11.1

Particle A is moving directly towards a gold nucleus.Particle B is moving along a line which passes close to a gold nucleus.Particle C is moving along a line which does not pass close to a goldnucleus.

(a) On Fig. 11.1, complete the paths of the α-particles A, B and C. [3]

(b) State how the results of such an experiment, using large numbers of α-particles, provides evidence for the existence of nuclei in gold atoms.

..........................................................................................................................................

..........................................................................................................................................

............................................................................................................................. .............

.................................................................................................................................... [3] [Total: 12]

11 (a) State, in terms of the particles in each nucleus, how the nuclei of two isotopes of the sameelement are different.

............................................................................................................................. ..................[1]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 3

P

83

83

83

(b) Fig. 11.1 shows a graph of nucleon number against proton number. The nucleus 212 Bi isplotted on the graph at the cross marked P.

213

212

nucleonnumber

211

210

209208

79 80 81 82proton number

83 84

(i) On Fig. 11.1,Fig. 11.1

1. plot a cross labelled Q for the nucleus formed when the 212 Bi nucleus emits anα-particle,

2. plot a cross labelled R for the nucleus formed when the 212 Bi nucleus emits aβ-particle.

[4]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 383

8383

(ii) The half-life for the decay of 212 Bi is 60minutes.

A sample of 212 Bi is placed at a fixed distance from a detector. The initialmeasurement of the count rate from the sample of 212 Bi is 2400 counts perminute.

Calculate the count rate from the sample 5.0 hours later.

count-rate = ...........................................................[2] [Total: 7]

5- A beam of ionising radiation, containing -particles, -particles and -rays, is travelling left toright across the page. A magnetic field acts perpendicularly into the page.

(a) In the table below, tick the boxes that describe the deflection of each of the types ofradiation as it passes through the magnetic field. One line has been completed, to helpyou.

ForExaminer’s

Use

MS.RAJA ELGADY/RADIOACTIVITY PAPER 3not

deflecteddeflectedtowards

top of page

deflectedtowards

bottom of page

largedeflection

smalldeflection

-particles ✓ ✓

-particles

-rays

[3]

(b) An electric field is now applied, in the same region as the magnetic fieldand at the same time as the magnetic field.

What is the direction of the electric field in order to cancel out the deflection of the-particles?

............................................................................................................................. ....... [2]

[6- (a) α-particles, β-particles and γ-rays are known as ionising radiations.

(i) Describe what happens when gases are ionised by ionising radiations.

............................................................................................................................. .....

..................................................................................................................................

............................................................................................................................. .....

(ii) Suggest why α-particles are considered better ionisers of gas than β-particles.

............................................................................................................................. .....

.................................................................................................................................. [3]

(b) (i) Suggest two practical applications of radioactive isotopes.

1. ................................................................................................... ...........................

2. ............................................................................................................................. .

(ii) For one of the applications that you have suggested, describe how it works, or drawa labelled diagram to illustrate it in use.

............................................................................................................................. .....

...................................................................................... ............................................

............................................................................................................................. .....

[4]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 37- (a) α-particles, β-particles and γ-rays are known as ionising radiations.

(i) Describe what happens when gases are ionised by ionising radiations.

............................................................................................................. .....................

............................................................................................................................. .....

..................................................................................................... .............................

(ii) Suggest why α-particles are considered better ionisers of gas than β-particles.

............................................................................................................................. .....

.................................................................................................................................. [3]

(b) (i) Suggest two practical applications of radioactive isotopes.

1. ................................................................................................... ...........................

2. ............................................................................................................................. .

(ii) For one of the applications that you have suggested, describe how it works, or drawa labelled diagram to illustrate it in use.

............................................................................................................................. .....

...................................................................................... ............................................

............................................................................................................................. .....

8- A radioactive source emits only β-particles.

(a) A scientist wishes to investigate the deflection of β-particles by an electric field. Draw alabelled diagram to suggest a suitable experimental arrangement.

[3]

(b) State how the apparatus would be used to show the deflection of the β-particles by theelectric field.

............................................................................................................................. .............

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MS.RAJA ELGADY/RADIOACTIVITY PAPER 3................................................................................

............................................................................................................................. ........ [2]

(c) State how the results would show the deflection of the β-particles.

............................................................................................................................. .............

...................................................................................................... ............................... [1]

(d) Explain the direction of the deflection obtained.

............................................................................................................................. .............

.............................................................................................................................. ....... [1]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 39- Fig. 11.1 shows an experiment to test the absorption of β-particles by thin sheets of

aluminium. Ten sheets are available, each 0.5mm thick.Examiner’s

Use

β-particle source

sheets ofaluminium

detector counter

Fig. 11.1

MS.RAJA ELGADY/RADIOACTIVITY PAPER 3(a) Describe how the experiment is carried out, stating the readings that should be taken.

............................................................................................................................. .............

..........................................................................................................................................

............................................................................................................................. .............

..........................................................................................................................................

............................................................................................................................. ....... [4]

(b) State the results that you would expect to obtain.

............................................................................................................................. .............

........................................................................... ...............................................................

............................................................................................................................. .............

.................................................................................................................................... [2] [Total: 610- A technician sets up a radiation detector in a university laboratory, for use in some experiments.

Even before the radioactive source for the experiment is brought into the laboratory, the detectorregisters a low count rate.

(a) Suggest what causes this count rate.

............................................................................................................................. ..................[1]

(b) A radioactive source that emits α-particles is placed on the laboratory bench and the sourceis gradually moved closer to the detector.

At first, the detector continues to register a low count rate sometimes slightly less than thecount rate registered without the source. The count rate suddenly increases to a very highvalue when the source is very close to the detector.

Explain these changes in the count rate.

............................................................................................................................. ......................

............................................................................................................................. ......................

................................................................................... ................................................................

............................................................................................................................. ......................

.............................................................................................................................................. .[3]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 3(c) In a second experiment, α-particles pass between two parallel, horizontal metal plates in a

vacuum.They then continue to the detector as shown in Fig. 9.1.

metal plate

_-particles

source detector

metal plate

Fig. 9.1

A positive charge is established on the upper plate and a negative charge on the lower plate.

(i) On Fig. 9.1, sketch the new path of the α-particles. [2]

(ii) State what happens to the count rate registered by the detector.

............................................................................................................................. ..............

...................................................................................................................................... .[1]

[Total: 7]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 311 Fig. 11.1 shows a beam of radiation that contains α-particles, β-particles and γ-rays. The

beam enters a very strong magnetic field shown in symbol form by N and S poles.

ForExaminer’s

Use

MS.RAJA ELGADY/RADIOACTIVITY PAPER 3N

beam ofradiation

S

Fig. 11.1

Complete the table below.

radiation direction of deflection,if any

charge carried byradiation, if any

α-particles

β-particles

γ-rays

[6]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 312- (a) Fig. 10.1 is the decay curve for a radioactive isotope that emits only β-particles.

400

ForExaminer’s

Use

count ratecounts /min 300

200

1000

0 10 20 30 40time /min

Fig. 10.1

Use the graph to find the value of the half-life of the isotope.

Indicate, on the graph, how you arrived at your value.

half-life …………………………. [2]

(b) A student determines the percentage of β-particles absorbed by a thick aluminiumsheet. He uses a source that is emitting only β-particles and that has a long half-life.

(i) In the space below, draw a labelled diagram of the apparatus required, set up tomake the determination.

[2]

(ii) List the readings that the student needs to take.

............................................................................................... ....................................

............................................................................................................................. ......

..................................................................................... ..............................................

............................................................................................................................. . [3]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 3

38

13- (a) Complete the table below for the three types of radiation.

radiation nature charge stopped by

γ electromagneticradiation

β negative

α thick paper

[3]

(b) An isotope of strontium is represented in nuclide notation as 90Sr.

For a neutral atom of this isotope, state

(i) the proton number, ...............

(ii) the nucleon number, ...............

(iii) the number of neutrons, ...............(iv) the number of electrons. ...............

[3]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 3(c) A sample of a radioactive material is placed near a radiation detector. A count-rate

of4800 counts /s is detected from the sample. After 36 hours the count-rate has fallen to

600 counts /s.

Calculate how many more hours must pass for the count-rate to become 150 counts /s.

number of hours = ............................................... [3] [Total:

9]

14- (a) Complete the following statements.

(i) An α-particle consists of ......................................................................................... .

(ii) A β-particle consists of ........................................................................................... .[3]

(b) As α-particles and β-particles pass through a gas, molecules of the gas become ionised.

Explain what is meant by the ionisation of a gas molecule.

..........................................................................................................................................

............................................................................................................................. ......... [1]

MS.RAJA ELGADY/RADIOACTIVITY PAPER 3(c) Fig. 11.1 shows a beam of α-particles and a beam of β-particles in a vacuum. The

beams are about to enter a region in which a very strong magnetic field is acting. Thedirection of the magnetic field is into the page.

ForExaminer’s

Use

20MS.RAJA ELGADY/RADIOACTIVITY PAPER 3_-particles

`-particles

uniform magneticfield

Fig. 11.1

(i) Suggest why the paths of the particles in the magnetic field arecurved.

................................................................................. .............................................

[1] (ii) Sketch the paths of both types of particle in the magnetic field.

[3] [Total: 8]

21MS.RAJA ELGADY/RADIOACTIVITY PAPER 315- (a) State the nature of γ-rays.

............................................................................................................................. ......................

............................................................................................... ............................................... [1]

(b) A beam of α-particles and β-particles passes, in a vacuum, between the poles of a strongmagnet.

Compare the deflections of the paths of the two types of particle.

...................................................................................................................................................

............................................................................................................................. ......................

............................................................................................................................. ................. [2]

(c) A beam of β-particles passes, in a vacuum, through the electric field between a pair ofoppositely charged metal plates.

Describe the path of the particles.

..................................................................................................... ..............................................

............................................................................................................................. ......................

.............................................................................................................................................. [2]

(d) The nuclear equation shows the decay of an isotope of polonium.

A 206 4ZPo 82Pb + 2X

22MS.RAJA ELGADY/RADIOACTIVITY PAPER 3(i) State the nature of X.

..................................................................................................................................... ......

........................................................................................................................... ...........[1]

(ii) Calculate the values of A and Z.

A = .................... Z = ..................... [1] [Total: 7]