203
Gelombang Elektromagnetik
B1=19 B5;9C1A ;H , :D71 497D1;1 ;?=D9;1B9 :1A1; :1D8 2525A11A92D;9?=5C5A41DCD;5;B5A9=5?581A19=DF1
497D1;1 DCD; CD:D1 B91A1 A579?1 B5417;1 497D1;1DCD;B91A19C5A1B9?1 81G1
=5=99;9A5C176A5;D5B91C1A1
HB1=19 HG1749;51 457175?=217545;5?=217545;497D1;1?58B5=D1
1G11A149?41?5A1C?ADCD;;?=D9;1B9:1A1;:1D8B91A141?5A1B9 A141ACA1B8?A9H?
,41+=D1941A9 HB1=19491C1B
H41497D1 ;1DCD;B91A1C55E9B941A149?:D71DCD;;?=D9;1B9C55?B5D5A
91C1B6A5;D5B99941C5=D;175?=217=9;A?5?=217 9925A1B141A911C11CAD=18C1771B55AC9?
5;CAD=B51:DCG114118B91A96A1=5A18B91AC1=1;41B91A DCA1E9?5C5=D491141B5;CAD=C5A1;89A1949C5=D;1B91A
41B91A D2D711C1A16A5;D5B91:1775?=217 41351C
A1=21C3181G114118
149?5=131A411C49C17;11416A5;D5B9
H5A111:17 75?=217A149?5=131A9CD
5 9;5C18D9
H
L H
L =B
+CD;=5G55B19;1G17D1;112-.;
c f
=1;1
c f
L
=B L
H
= 1491:1775?=217A149?5=131A14118
=
c f
K 5C5A171
351CA1=21C3181G1L =B
1:1775?=217=5C5A 6A5;D5B985ACH
Tes Kompetensi Subbab
A
1+.,,-4+4,3.
1G1749=1;BD4457175?=21755;CA? =175C9;15A25411G1457175?=217
=5;19; 1G1749=1;BD44571B5;CAD=75?=217
55;CA?=175C9; 141B5;CAD=75?=21755;CA?=175C9;
C5A411C25A=131==131=:59B75?=217 G17 492541;1 25A41B1A;1 6A5;D5B9G1
51B;1B5C91B5;CAD=25B5AC119;1B9G1 411=C5;??79
5CD;118 1:17 75?=217 55;CA? =175C9; 49 411= AD17 81=1 :9;1 49
;5C18D96A5;D5B975?=217C5AB52DCH
Contoh
9.1
Kata Kunci
• gelombang elektromagnetik
• spektrum
• Extra Low Frequency ELF
• Very Low Frequency VLF
• Medium Frequency MF
• High Frequency HF
• Very High Frequency VHF
• Ultra High Frequency UHF
• sinar inframerah
• sinar tampak
• sinar ultraviolet
• sinar-X
• sinar gamma
204
Mudah dan Aktif Belajar Fisika untuk Kelas X
a. Sistem AM Amplitudo Modulasi
5?=2172DG925A6A5;D5B9A54184921F1?5875?=217A149? G1725A6A5;D5B9C97791;5C75?=217C5AB52DC49131A;1=51D9
75?=217A149?B5217195AD21811=9CD4?5?=217A149?=5=99;9 1=9CD4? G17 25A25412541 B5BD19 4571 75?=217 2DG9 G17
4921F1G1 4571 6A5;D5B9 75?=217 A149?G1 C5C1 ?4D1B9 1=9CD4?141131A1A149?49D;9B;1141-1
5?=217BD1A1G174921F1?5875?=217A149?B5217191;921C 5AD21811=9CD4?411C4571=D418491CD;1?5819B19??B65A
G19CD19B117;1B1G17=5714D7=D1C19BCA9;131A1A149? 411C=5:17;1DC5=1CC5=1CG17:1D81CD175?=217A1
49?14119B19??B65A495A981C;1141-1 b.
Sistem FM Frekuensi Modulasi
5?=2172DG94921F1?5875?=21755;CA?=175C9;411= 25CD; =?4D1B9 6A5;D5B9 49 =11 6A5;D5B9G1 25AD218D218 41
1=9CD4?G1 C5C1 9BC5= 99 =5=99;9 ;55=181 G1;9 :1A1; :17;1D1G1G17C5A21C1BB5212BD;1A491CD;1?4D1B96A5;D5B9
1415=131AA149?49D;9B;1141-1 9BC5==5=99;9;D19C1BBD1A1G17219;412521B41A99C5A65A5B9
G17=5ADB1;B9G1B9G16A5;D5B975?=217C5C19=D418=5711=97177D 1;59BCA9;149D41A141C941;411C491CD;1?5819B19??B65A
58;1A5175?=217C941;411C491CD;1?5819B1 9??B65A 1;921CG1 75?=217 99 C941; 411C =53119 C5=1C
C5=1CG17:1D858B52129CD492DCD8;1BC1B9DBC1B9D578D2D7 A519G17411C=5=131A;1;5=21975?=21775?=217G17
49C5A9=1G1171A:1A1;:17;1D1G1B5=1;9=5D1BC1B9DBC1B9D 578D2D7C5AB52DC49D;9B;1141-1
Gambar 9.3
Pantulan gelombang radio oleh ionosfer.
Gambar 9.4
Modulasi frekuensi pada radio pemancar FM.
Bumi gelombang
radio ionosfer
Gambar 9.2
Modulasi amplitudo pada pancaran radio AM.
411BC9=575C18D9A149?41A149?2D;15AB1=1;5?=?;251:1A 4131A91896?A=1B9=5751911G1749=1;BD4A149?41A149?1
5A25411491C1A1;54D1G14121719=11:17;1D16A5;D5B9;54D1:59B A149?C5AB52DC 9;1495AD;125A;D:D718;5B118B1CDBC1B9D49415A1841
D1C181?A141A9;5791C19941;D=D;1CD71BC5AB52DC;51417DAD41
Mari Mencari Tahu
Gambar 9.5
Untuk mengirimkan gelombang FM diperlukan antena pemancar.
B. Jenis-Jenis Gelombang Elektromagnetik
1. Gelombang Radio
5?=217A149?=5AD1;175?=21755;CA?=175C9;41=5A1=21C 4571;5351C13181G1G19CDL
=B5?=217A149?=5=99;9 415A186A5;D5B91C1A1
HB1=19 H41497D1;1B52171911C
;?=D9;1B91C1D5=21F196?A=1B941A9BD1CDC5=1C;5C5=1C19 961C75?=217A149?=D418491CD;1?5819B19??B65AD=9
B58977175?=217A149?411C=53119C5=1CC5=1C49D=9G17 :1A1;G1B171C:1D841A95=131AA149?
5?=217A149?497D1;1411=B9BC5=5=2931A11:1A1;:1D8G17 C941; =577D1;1 ;1F1C 5781C1A 5?=217 55;CA?=175C9;
25AC941;B5217195=21F175?=2171D49?BD1A1414D1=131= 31A1DCD;=5=21F175?=2172DG9;555A9=1G1G19CD4571B9BC5=
1=9CD4?=?4D1B941B9BC5=6A5;D5B9=?4D1B941
