Diagram 12.1 shows a building with a lightning conductor.
Rajah 12.1 menunjukkan sebuah bangunan yang mempunyai pengalir kilat.
Diagram 12.1 / Rajah 12.1
The function of the lightning conductor is to attract lightning towards
it. In order to increase the chances of lightning striking the lightning
conductor, some radioactive substance is sometimes placed at the tip of the
lightning conductor. The radioactive substance will emit radiations which
ionize the air around it. The ions provide a conducting region in the air and
this will help attract the lightning bolt.
Fungsi pengalir kilat ialah
untuk menarik kilat kepadanya. Untuk meningkatkan keberangkalian kilat memanah
pengalir kilat ,satu bahan radioaktif telah diletakkan dihujung pengalir kilat
tersebut.Bahan radioaktif tersebut akan memancarkan sinaran dimana ia akan
mengionkan udara disekelilingnya.Pengionan ini akan menwujudkan satu kawasan
bercas yang akan membantu menarik kilat.
Table 12.1
shows the characteristics of five radioactive substances which may be used in
the lightning conductor for the purpose describe above.
Jadual 12.1 menunjukkan ciri-ciri lima bahan
radioaktif yang digunakan pada pengalir
kilat untuk tujuan yang diterangkan di atas.
( a )
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( i)
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What is the structure of a beta particle ?
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Apakah struktur zarah
beta?
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[2
marks / markah]
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( ii)
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You are assigned to study the characteristics of some radioactive
substances that are suitable for use in lightning conductor as in diagram
12.1.Explain your choice.
Anda ditugaskan untuk
mengkaji ciri-ciri beberapa bahan radioaktif yang sesuai untuk digunakan
dalam pengalir kilat seperti dalam rajah 12.1. Terangkan pilihan anda.
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[6 marks/markah]
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(iii)
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Determine the most suitable radioactive substance to be used and give
one reason for your choice.
Tentukan bahan radioaktif
yang paling sesuai untuk digunakan dalam pengalir kilat dan berikan sebabnya.
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[2
marks / markah]
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(b)
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Technitium – 99 m is radioactive substance which is commonly used in
medical diagnosis to detect defects in bones ,heart,kidneys and other organs.
It has a half life of 6 hours and it emits low energy gamma rays.Based on the
information given about Technitium-99 m ,explain why it is suitable for
medical diagnosis.
Technitium – 99 m ialah
bahan radioaktif yang digunakan dalam bidang perubatan untuk tujuan mengesan
kecacatan pada tulang,hati,buah pinggang dan sebagainya.Ia mempunyai separuh
hayat selama 6 jam dan memancarkan sinar gamma yang bertenaga
rendah.Berdasarkan maklumat yang diberikan tentang Technitium-99 m,terangkan
mengapa ia sesuai digunakan dalam bidang perubatan.
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[5 marks /
markah]
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(c)
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Diagram 12.2 shows the rate of activity of a radioactive substance against time
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Rajah
12.2 menunjukkan kadar aktiviti satu
bahan radioaktif melawan masa.
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(i)
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From the graph, determine the half life of the radioactive substance.
Daripada graf , tentukan
separuh hayat bahan radioaktif
diatas.
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[2 marks /
markah]
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(ii)
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If the
initial mass of radioactive substance is 5 g ,calculate the mass of the
radioactive substance which decays after 45 minutes using the half-life you
have determined in (c) i.
Jika jisim asal bahan radioaktif ialah 5 g,kirakan
jisim bahan radioaktif tersebut selepas 45 minit ia mereput dengan mengunakan
separuh hayat yang kamu perolehi dalam (c)i.
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[3 marks /
markah]
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Half life of 6 hour is a short
half life. Within one day almost all of the substance injected into the body
will have lost its activity.
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It can then be safely excreted
from the body without causing unnecessary damage to the tissues.
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Since it is a gamma emitter, the
radiation can come out of the body because gamma is very penetrating. Hence
it can be traced from the outside using the detector.
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Since it is low energy gamma
radiation will not do much damage to the tissues while it is going through
the body
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Hence this is very suitable for
use in medical diagnosis.
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1200 – 600 – 300 – 150 – 75 = 4 T1/2
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T ½ = 15 minutes
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5 g – 2.5 g ( 15 minutes ) – 1.25
g ( 30 minutes ) – 5/8 g (45 minutes )
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5 – 5/8 g
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35/8 g
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