111
Cahaya dan Optika
A C
B B
D s
s benda
bayangan
5A41B1A;18D;D=5=1CD149C9C9;25A1;D
1
i
1
r
1
r
J 1491A18B91A1CD?5835A=9=5=25CD;BD4DCJC5A814171A9B?A=1
a. Pemantulan pada Cermin Datar
1H1741981C14135A=941C1A;5C9;14125A49A949451 35A=941C1AC5AB52DC14135A=9C5A981C14121H17141 1719=11
B961C21H171H17C5A25CD;14135A=941C1A 5A81C9;104
-9C9;,=5AD1;121H17141A9C9C9;, 41
DA?B5B5=25CD;121H17114135A=941C1A14118B52171925A9;DC ,91A41C17,
B91A:1CD814135A=941C1A4571BD4DC41C17
1
;5=D491B91A99491CD;1 5A81C9;1:11B91A ,91A41C17,
B91A
:1CD814135A=94571BD4DC41C17
2
;5=D491B91A99491CD;1 5A81C9;1:11B91A 5A1:171B91A1CD41B91A1CD
49251;1735A=9
49D;9B;1457171A9BC5ADCDBDCDB4125A?C?7149C9C9; 1495C1;21H171C9C9;14118H174925CD;41A95A?C?71
5A1:1714D1B91A1CD 57131A1H17B1=121H17125414D149=5B941C97149=5B9
411CC5A25CD;?5835A=941C1A A?B5B5=25CD;121H171H1B1=1 B55AC91412541C9C9; 1H17C5A5C9714118411=B5C91A?B5B
5=25CD;121H1718D;D=5=1CD1B51D25A1;D 5A81C9;104
25A9;DC
.CD;2541H172D;125AD1C9C9;1C1D71A9B411;1=5411C ;1218F1D;DA121H17125415AB9BB1=14571D;DA12541H1
5414121H17181H125A2541411=811A18;9A941;11H1 5A81C9;1 04
1791 ;9A9 2541 =5:149 21791 ;11
21H17141B5219;H1 5A9BC9F19949B52DC5=219;1B9B90. +2.,+58;1A51141H15=219;1B9B999CD9B1H178541;
492131=51D935A=95D9B18DAD6H181ADB49219; 5A41B1A;121H171254114135A=941C1A411C49B9=D;1
218F1B961C21H1712541H174925CD;?5835A=941C1A14118 B52171925A9;DC
K =1H1 K D;DA1B1=125B1A4571D;DA12541
K C571; K :1A1;2541C5A814135A=9B1=14571:1A1;21H171C5A8141
35A=9
Gambar 6.5
Ukuran benda persis sama dengan ukuran bayangan
Gambar 6.4
Pembentukan bayangan pada cermin datar
bayangan S
S P
1
P
2
benda
1
2
Gambar 6.6
Ketika bercermin, posisi kiri benda menjadi posisi kanan bayangan
mata pengamat
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112
Mudah dan Aktif Belajar Fisika untuk Kelas X
58;1A51B91A1CDB1=14571 B91A41C17=1;1
149DCD;411C=5981C21H171 B5DAD8 CD2D8 495AD;1 1:17
35A=941C1A=99=1 41A9C9779
CD2D8B5B5?A17
:111:61:110: 1H171H1C11411821H171H17C5A25CD;41A95A?C?7117
BD7B91AB91A3181H1B5417;121H171=1H11411821H171H17 4981B9;141A95A?C?715A1:171B91AB91A3181H1 ,5217193?C?8
21H171H174981B9;114135A=941C1A=5AD1;121H171=1H1 ;1A51 21H171 C5AB52DC =5AD1;1 5A?C?71 17BD7 41A9
5A1:171B91AB91A3181H1 41D3?C?821H171H1C1C5A:149 14121H171H174981B9;1?58A?H5;C?A1411H1A
9CD71:17=99=D=BD1CD35A=9H17492DCD8;1171AB5?A1751A9141C 411C=5981CB5DAD8CD2D8H1H17C9779H1=5C5A
9 5A81C9;171=21A25A9;DC
70+:112+77+40,164 5A81C9;1 04
:9;1 B52D18 2541 25A141 49 451 4D1
2D1835A=9H17=5=25CD;BD4DCB1CDB1=1191;1C5A25CD; B5:D=18 21H171 D=18 21H171 25A71CD7 141 25A11 25B1A
BD4DC 5A41B1A;181B95;B5A9=5:D=1821H171H174925CD; ?584D12D1835A=9H17=5=25CD;BD4DC 14118B52171925A9;DC
,52D182541C5A5C1;49451
2D1835A=941C1AH17=5=25CD;BD4DCJ 9CD7:D=1821H171H17C5A25CD;
9 9;5C18D9
J +
360 1
+
J L J
+ L 149 :D=1821H171H17C5A25CD;2D18
J L
+ 5C5A171
+
:D=1821H171 BD4DC1C1A14D12D1835A=9
L
Contoh
6.3
G F
H E
A D
C B
cermin
Gambar 6.7
Benda yang diletakkan di antara dua buah cermin datar dan membentuk
sudut 90° akan menghasilkan 3 buah bayangan.
cermin I
cermin II
bayangan
bayangan bayangan
benda
Contoh
6.2
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113
Cahaya dan Optika
Gambar 6.8
Bagian-bagian cermin cekung f = jarak fokus
R = kelengkungan cermin R
f O
B F
P
a b
c P
F O
Gambar 6.9
Sinar istimewa pada cermin cekung
Gambar 6.10
Pembentukan bayangan di ruang III AB pada cermin cekung
O B
F P
A A
B I
II III
5A41B1A;104
04
4104
411C 49B9=D;1218F1
1 :9;1 2541 141 AD17 =1;1 21H171 H17 4981B9;1 14118 =1H1C571;41495A25B1A
2 :9;1254125A14149AD17=1;121H171H174981B9;114118 H1C149AD17C5A219;41495A25B1A
3 :9;1254125A141141AD17=1;121H171H174981B9;1 14118H1C149AD17C5A219;41495A25B1A
Gambar 6.11
Gambar bayangan jika letak bendanya di ruang II
Gambar 6.12
Gambar bayangan jika bendanya di ruang I
O A
P A
B B
I II
III
F O
F A
P A
B B
I II
III
S S
b. Pemantulan pada Cermin Cekung