Mudah dan Aktif Belajar Fisika untuk Kelas XII
264
B. Radioaktivitas
1. Sejarah Penemuan Radioaktif
;7B7 H7:?E7AJ? ?D? :?J;CKA7D EB; +48 +7;+8+2 F7:7 I;97H7 J?:7A I;D=77 7 I;:7D= C;D;B?J? I?7J
:7D + F7:7=7H7CKH7D?KCN7D=:?I?D7H?:;D=7DI?D7H2
++ 0 + + ?I7BDN7 F7:7 H7C8KH7C8K B7BK B?DJ7I N7D= 8;HI?D7H ?A7
J;HA;D7 IEHEJ7D B7CFK 7H7C KH7D?KC N7D= :?F;H=KD7A7D +7;+8+2 :?B;J7AA7D F7:7
8KD=AKI7DFB7JEIEH;I;DI?:7D:?;CKH:?87M7I?D7H7J77H? ;J?A7 FB7J EIEH;I;DI? :?9K9? 7J7K :?FHEI;I F7:7 ?BC D;=7J? J;HDN7J7 J;H:7F7J
FEB7 ?J7C I;IK7? 8;DJKA AH?IJ7BDN7 +7;+8+2 C;DN?CFKBA7D 87M7 H7:?7I?N7D=C;D=?J7CA7DFB7JFEJH;J8KA7DB78;H7I7B:7H?977N7BK7H
C;B7?DA7D8;H7I7B:7H?=7H7C?JKI;D:?H? B;I;878?JK=;7B7?D?:?I;8KJ =;7B7 H7:?E7AJ? 7J7K H7:?E7AJ?L?J7I
2. Jenis-Jenis Radioaktif
7H? F;D;CK7D +7;+8+2 87DN7A ?BCKM7D N7D= A;CK:?7D C;D;B?J? J;DJ7D= I?D7H H7:?E7AJ? ?D? I7B7 I7JKDN7 7:7B7 84+9: ;:.+8,58 7:7
?7 :;D=7D FEIJKB7JDN7 C;DN7J7A7D 87M7 H7:?E7AJ? 8KA7D 7DN7 :?I;878A7D EB; F;HK877D N7D= 8;HI?7J 7JEC?I C;B7?DA7D F;C7D97H7D
H7:?E7AJ? 8;HB7D=IKD= 8;HI7C77D :;D=7D F;HK877D J;HI;8KJ ;:.+8,58 C;CF;HB?7JA7D7:7DN7:K7C797CH7:?7I?N7D=A;BK7H:7H?KH7D?KC:;D=7D
97H7 C;D=KAKH AK7J 7HKI B?IJH?A N7D= J?C8KB EB; 7:7DN7 ?ED?I7I? K:7H7
7:7 8+ ;8+ :7D IK7C?DN7 +88+ ;8+ C;D;CKA7D
:K7 KDIKH H7:?E7AJ? N7D= :?I;8KJ FEBED?KC :7D H7:?KC ;H:7I7HA7D J;H7:?DN7 I?D7H H7:?E7AJ? ?D? C7A7 H7:?E7AJ?L?J7I :7F7J :?8;:7A7D
C;D7:? :K7 A7J;=EH? 7DJ7H7 B7?D 7
H7:?E7AJ? 7B7C?7 N7?JK F;C7D97H7D I?D7H H7:?E7AJ? N7D= J;H7:? I;97H7 IFEDJ7D 7A?87J J?:7A IJ78?BDN7 ?DJ? 7JEC
8 H7:?E7AJ? 8K7J7D N7?JK F;C7D97H7D I?D7H H7:?E7AJ? N7D= 8;H7I7B
:7H? ?DJ??DJ? IJ78?B N7D= :?=7D==K A;IJ78?B7DDN7 :;D=7D 97H797H7 J;HJ;DJK ?D==7 C;D7:? ?DJ? N7D= J?:7A IJ78?B
-7B7I7JK;D?IH7:?7I?N7D=CK:7:?I;H7F7:7B7I?D7H7B7 ,7:?7I?
B7?DN7D=C;C?B?A?:7N7J;C8KIB;8?8;I7H:?D7C7A7DI?D7H8;J7 I;HJ7
I;8K7 F7D7D= =;BEC87D= N7D= F;D:;A :?I;8KJ I?D7H =7CC7 D:7 :7F7J C;D=;J7K? A7H;AJ;H?IJ?A I?D7H
I?D7H :7D I?D7H C;B7BK? F;C8?7I7D H7:?7I? :;D=7D J78KD= ;?=;H KBB;H ;H7J?A7D
38
;J?A7 IKC8K H7:?E7AJ? :?J;CF7JA7D F7:7 I7B7 I7JK KKD= C;:7D C7=D;J :7D J78KD= F7:7 KKD= N7D= B7?D J;HDN7J7 I?D7H
:?8?7IA7DA;F?H?D=7DD;=7J?:7DI?D7H 7A7D:?8?7IA7DA;F?H?D=7DFEI?J?
7:? :7F7J :?I?CFKBA7D 87M7 I?D7H 8;HCK7J7D FEI?J?
7J7K ;
I?D7H 8;HCK7J7DD;=7J?
7J7K ; I;:7D=A7DI?D7H D;JH7B
;H?AKJ ?D? 7A7D :?;B7IA7D F;C7D97H7D I?D7H 7B7 I?D7H 8;J7
:7D I?D7H =7CC7
a. Pemancaran Sinar Alfa
7II7 C7KFKD CK7J7D I?D7H 7B7 ?:;DJ?A :;D=7D ?DJ? ;B?KC ; ?A7 IK7JK O7J H7:?E7AJ? C;C7D97HA7D I?D7H 7B7 DECEH 7JEC O7J ?JK
Gambar 10.6
Dalam medan magnet, hanya sinar yang tidak dibelokkan.
sumber radioaktif
radium sumber
magnet kuat
ratemeter P
Q
Gambar 10.5
Pengujian pembiasan sinar dalam medan magnet.
Sumber: Physics for ‘O’ Level, 1990
Sumber: Conceptual Physics, 1998
DIUNDUH DARI: WWW.BUKUPAKET.COM Sumber buku bse.kemdikbud.go.id
Fisika Inti dan Radioaktivitas
265
7A7D 8;HAKH7D=
:7H? DECEH 7JEC ?D:KADN7 :7D DECEH C7II7DN7 7A7D 8;HAKH7D= -;97H7KCKCH;7AI?F;C7D97H7D7B7
:7F7J:?JKB?IA7D I;87=7? 8;H?AKJ
2 2
EDJE 2
b. Pemancaran Sinar Beta
K7J7D :7D C7II7 I?D7H I7C7 :;D=7D ;B;AJHED 7B ?D? A7H;D7
I?D7H 8;J7 J?:7A B7?D 7:7B7 ;B;AJHED :?8;H? B7C87D= 7J7K
; -;IK7?:;D=7DKAKC;A;A7B7DECEH7II7:7DECEHJECIK7JK
?DJ??D:KAN7D=I;97H7IFEDJ7DC;C7D97HA7DI?D7H 7A7DC;D=7I?BA7D
?DJ?7D7AN7D=DECEHC7II7DN7J;J7F:7DDECEH7JECDN78;HJ7C87I7JK -;97H7 KCKC H;7AI? F;C7D97H7D
:?JKB?I I;87=7? 8;H?AKJ 2
3 ,
EDJE ,
:;D=7D , 7:7B7 D;KJH?DE
c. Pemancaran Sinar Gamma
;H8;:7 7BDN7 :;D=7D F;C7D97H7D I?D7H :7D I?D7H N7D=
C;C7D97HA7D F7HJ?A;B 8;HCK7J7D F;C7D97H7D I?D7H 8KA7DB7 8;H8;DJKA F7HJ?A;B J;J7F? =;BEC87D= ;B;AJHEC7=D;J?A ?A7 F7:7
F;C7D97H7D I?D7H :7D J;H7:? F;HK877D IJHKAJKH KCB7 FHEJED
:7DD;KJHEDF7:7F;C7D97H7DI?D7H J;H7:?F;HK877DIKIKD7DF7HJ?A;B F7HJ?A;B F;C8;DJKA ?DJ? 7JEC -?D7H J?:7A C;C?B?A? C7II7 C7KFKD
CK7J7D B; A7H;D7 ?JK DKAB?:7 J;H;AI?J7I? N7D= C;C7D97HA7D I?D7H J?:7A C;D=7B7C? F;HK877D DECEH 7JEC C7KFKD DECEH C7II7
;C7D97H7D I?D7H :?7M7B? EB; ?DJ? ?D:KA N7D= I;97H7 IFEDJ7D
C;C7D97HA7D I?D7H :7D C;C8;DJKA ?DJ? 87HK
N7D= 8;H7:7 :7B7C A;7:77D;AI?J7I? -;B7DKJDN7?DJ?87HK:7B7CA;7:77D;AI?J7I??D?I;97H7
IFEDJ7D C;C7D97HA7D I?D7H KDJKA C;D7:? ?DJ? IJ78?B FHEI;I
F;HK877D ?D? :?JKDKAA7D F7:7 38 ,;7AI? ?DJ? F;C7D97H7D I?D7H ?D? 8?7I7DN7 :?JKB?I I;87=7? 8;H?AKJ
2 3
EDJE ;I?CFKB7D:7H?A7H7AJ;H?IJ?AI?D7HH7:?E7AJ?N7?JKI?D7H
I?D7H :7D I?D7H :?JKDKAA7D F7:7 +2 7N7 J;C8KI I?D7H
I?D7H :7D I?D7H C7I?D=C7I?D= :?JKDKAA7D F7:7 38
– –
1,015 MeV
0,834 MeV
Gambar 10.7
Pemancaran dan
dalam peluruhan
27 12
Mg dan
27 13
Al .
Carilah informasi mengenai pemanfaatan sinar
, , dan
.
Tugas Anda 10.1
sumber radioaktif kertas
aluminium
timbal
Gambar 10.8
Daya tembus partikel ,
, dan .
27 12
Al
27 12
Al
+2
7H7AJ;H?IJ?A-?D7H,7:?E7AJ?
;HJ7IJ?F?I KB?JC7DKI?7
BKC?D?KCCC .?C87BJ?F?I
+4948 51:,
+1923. 99
+39423 +4-4+:
+336;4 +3;9
;:4 B7
;J7 7CC7
DJ?;B?KC B;AJHED
,7:?7I?;B;AJHEC7=D;J?A EI?J?
;=7J? .?:7A8;HCK7J7D
;9?B ;I7H
.?:7A:?8?7IA7D ;I7H
,;D:7 .?:7A8;HC7II7
Sumber: Conceptual Physics, 1998
Sumber: Physics for ‘O’ Level, 1990
DIUNDUH DARI: WWW.BUKUPAKET.COM Sumber buku bse.kemdikbud.go.id
Mudah dan Aktif Belajar Fisika untuk Kelas XII
266
3. Pelemahan Intensitas Sinar Radioaktif
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