Fisika Inti dan Radioaktivitas
263 =
?A;J7K? IC7
IC7 IC7
5 P
P 6;0
IC7
5
PP
6;0
IC7 IC7;0
IC7
;0
7:?;D;H=??A7JF;HDKAB;EDDN7 ;0
;0
-;C7A?D8;I7H;D;H=??A7JH7J7H7J7F;HDKAB;ED A;IJ78?B7DDN77A7DI;C7A?DJ?D==?A7H;D7:?F;HBKA7D
;D;H=? N7D= 8;I7H KDJKA C;C8ED=A7HDN7 H7?A ;D;H=? ?A7J F;H DKAB;ED J;H7:7F DECEH C7II7
8;H87=7? ?DJ? :7F7J D:7 F;H7J?A7D F7:7 38 ;H:7I7HA7D=H7?AJ;HI;8KJ:7F7J:?I?CFKBA7D
87M7 7
KDJKA 7H=7 N7D= A;9?B ;D;H=? ?A7JDN7 A;9?B
:7D D7?A 9;F7J I;IK7? :;D=7D F;HJ7C877D 8
KDJKA 7H=7 :?I;A?J7H ;D;H=? ?A7J
C7AI?CKCDN7 7CF?H J?:7A 8;HJ7C87 N7?JK ;0:7DJKHKDC;D7:?;0KDJKA
9 KDJKA7H=7
:?7J7I;D;H=??A7JDN7JKHKD ?D==7 C;D97F7? ;0
6. Gaya Inti
7N7?DJ?8;HI?7JI7B?D=C;DEB7AF7:77D=A7K7DI7D=7JF;D:;A:7D I7B?D= C;D7H?A F7:7 7H7A DKAB;ED N7D= 7=7A 7K ?A7 J?:7A :;C?A?7D
DKAB;ED :7B7C ?DJ? 7A7D C;DN7JK -?7JI?7J =7N7 ?DJ? 7DJ7H7 B7?D 7
=7N7 ?DJ? C;C?B?A? FH?DI?F :7I7H N7D= 8;H8;:7 :;D=7D =7N7 =H7L?J7I? C7KFKD =7N7 9EKBEC8
8 =7N7 ?DJ? J?:7A 8;H=7DJKD= F7:7 CK7J7D B?IJH?A I;?D==7 8;I7HDN7
=7N7 7DJ7H7 FHEJEDFHEJED 7J7K D;KJHED 7:7B7 I7C7 9
=7N7 ?DJ? 8;A;H7 F7:7 7H7A N7D= I7D=7J F;D:;A N7?JK I;A?J7H
P
C7J7K;HC? :
=7N7 ?DJ? I7D=7J 8;I7H I;?D==7 :?F;HBKA7D ;D;H=? I;8;I7H ;0 KDJKA C;C?I7A7D :K7 8K7 ;B;AJHED
Gambar 10.4
Grafik energi ikat per nukleon terhadap nomor massa berbagai
inti.
Kata Kunci
• isotop • hipotesis proton-elektron
• hipotesis proton-neutron • nomor atom
• nomor massa • nuklida
• defek massa • energi ikat inti
;B7IA7D:;D=7DI?D=A7J;;AF;D==78KD=7DDKAB;ED J;H7:7FC7II7?DJ?7JECN7D=J;H8;DJKA
.;DJKA7D87DN7AFHEJEDD;KJHED:7D;B;AJHED:7B7C 7JEC7JEC8;H?AKJ
7
;
:
,8
8 -?
;
C
9
B
7II7?DJ?
=
7:7B7
IC7 7II7DKAB;ED 8;87I7:7B7C7II7FHEJEDIC7:7DC7II7D;KJHED
IC7 IC7;0
Tes Kompetensi Subbab
A
+80142.6;1;2:.4
7 .;DJKA7DIKIKJC7II7DN7:;;AC7II7
8 .;DJKA7D;D;H=??A7J?DJ?DN7
7 D;H=? ?A7J
;
7:7B7 ;0 7H?B7 C7II77JECDN7
8 7D7A7?DJ?N7D=B;8?C7DJ7F
?
7J7K
?
; 7J7K ;
7H?B7:;;AC7II7;D;H=??A7J?DJ?:7D;D;H=??A7J F;HDKAB;EDKDJKA7JEC
BA, MeV per nukleon
nomor massa A 200
100 5
1 0
2
H
6
Li
9
Be
11
B
14
N
19
F
75
As
125
Te
4
He
12
C
20
Ne
35
Cl
56
Fe
89
Y
110
Cd
141
Pr
160
Dy
197
Au
180
Hf
209
Bi
238
U
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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
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