126
Mudah dan Aktif Belajar Fisika untuk Kelas X
8. Lensa
3A3:62793:=?538926B:B2023?A356=?5 =?5.B72?0B26;353:2;355B9:3
A77:38B50E9275B93057057BA;:A:A 33?A79;3?A3?==5;79?=9=?=E39A=?291;A3;B:A
A3?30BA5A3A75203?5B2:;93672B:369?37AB ;3;6;774A74A3;072:35A3A75
32:60320375E5270A7=:362B3?;B9:359B5 3?;B9;3:359B5A3?30BA;3?B90573?;B90=:3
E523;7972730BA:343?73?;B9:343?72A03?B932B E13;0B5932BE139B5AB50B513;0B52139B5
343?7A3?27?7A2B837E7AB:313;0B52:3139B5 313;0B59=C39AB:39=C3?532:6:3E5057
A356E:3076A30:2?72057A37E37703?74A;35B;B: 903?97?-1 2B:3139B59=94AB:3
27C3?532:6:3E5057A356E:3076A772?72057 A37E37703?74A;3E30?903?97?-1
303:B;:30768B6;3;6;743=;343=;3E5A3?8272 :326?B;353A6B7057057:32350792
:3A3?2ABA=A79A7A794=9B2BA93:359B5:3 -1 ;3;3?:76A993;30B6:32057057E
a. Pembiasan Cahaya pada Lensa Cembung
6EE58AB623?;B9:313;0B59;35:;7 3;073?903?97?2A59270793675503?9
03?97?07E;35B;B:3?6A79-1 57:3E5A30:9;356;0A16E:30760E92?7
2057:3E5A77:369?313A?;0A16E272:; :3:30769317:2?7227B2?03?903?97?079;35B;B:
AB:6300E:313;0B503?74A9=C3?53 .12.123-50,.2-4.
E5032=:36:313;0B52A2703AB92351? ;355;0?97?7?7A7;3DE7?7?7A7;3D2:3
13;0B52A750B6E7AB305703?79BA 7?E52A5388?B;0BBA;27079;3::B7A7A794=9B
9A74 :3
0 7?E52A5E5;3::B7A7A794=9B74 27079388?
B;0BBA; 1 7?E52A5;3::B7BA=A79A729;35:;73;07
Gambar 6.30
Lensa cembung bersifat konvergen mengumpulkan cahaya
Gambar 6.31
Lensa cekung bersifat divergen menyebarkan cahaya
Gambar 6.32
Bagian-bagian lensa cembung dan lensa cekung
33ABB2BA23C77;77;B;;355B93?; =
K K
I =
K
II
Keterangan: O = pusat optik
OF
1
= jarak fokus dari pusat optik OP
1
= jari-jari kelengkungan lensa F
1
dan F
2
= titik fokus P
1
dan P
2
= pusat kelengkungan lensa
Gambar 6.33
Sinar-sinar istimewa pada lensa cembung
F
1
F
1
F
1
F
2
F
2
F
2
a
b
c F
2
F
1
P
2
P O
F
2
F
1
P P
1
O
Di unduh dari : Bukupaket.com
127
Cahaya dan Optika
F
2
F
1
A B
O ruang
benda I I I
ruang benda
I I ruang
benda I
ruang benda
IV ruang
bayangan IV
ruang bayangan
I ruang
bayangan III
ruang bayangan
II
Gambar 6.34
Penamaan ruang pada lensa cembung
.+0-.34+.6..0,.2-4. ,AB9;3;3?;B263;03AB90E5?B52723227
03:95:327057;38270303??B533?A72-1 03?79BA
3A3?5 2-2:6=;=??B50322-
2:6=;=??B50E5 3A7:3;3;7:7972B0B6A7A794=9B27303:697?729E
?9 932B 4=9B A3?30BA ; 3?6A79 -1 BAB9 ;355;0?90E5032E52767:9=:36:313;0B5
27:9B91?305703?79BA 7:B972B0B67?7A7;3D2:313;0B5
0 7?3::B2A52?73?;B9:32270799303:95:3 1 3?=A=5A?2B7?07;3?B9:3A90E579
3?=A=5272A2?73?857?070E503?74A ;E227:B9792355?7BABBAB
b. Pembiasan Cahaya pada Lensa Cekung
3?032235:313;0B5:3139B503?74A;3E30?9 03?97?3?97?E58AB623?;B9:3139B59
2707931?;3E30? .12.123-50,.2+4.
2:3139B58B5A3?2A7?7?7A7;3DE503?5B 0573;03AB90E57?7?7A7;3D2:3139B5
2:6305703?79BA-1 7? E5 2A5 388? B;0B BA; 27079 399
03?:2?7A7A794=9B 0 7?E52A5;3B8BA7A794=9B
27079388?B;0BBA; 1 7?E52A5;3::B7BA=A7927A3?B9A729;35:;7
3;07 .+0-.34+.6..0,.2+4.
3?6A79-1
,AB9;355;0?90E5032 E52767:9=:36:3139B527:9B91?305703?79BA
7:B972B0B67?7A7;3D:3139B5 0 7?3::B2A52?73?;B9:32270799303:95:3
1 32E527:3A992723:3139B53::B;3567: 0E5E5;3;7:79774A;EA359273?9317:2A3?:3A9
2723:3139B5
Gambar 6.36
Sinar-sinar istimewa pada lensa cekung
F
1
F
2
F
1
F
2
F
1
F
2
Gambar 6.35
Pembentukan bayangan oleh lensa cembung
Gambar 6.37
Pembentukan bayangan oleh lensa cekung
a
b
c
F
2
F
1
A O
B A’
B’ s’
f s
h h’
Di unduh dari : Bukupaket.com
128
Mudah dan Aktif Belajar Fisika untuk Kelas X
K
30B6:3A77;3;7:797723907270A7=:363?;B913;0B52 139B5A7327:3A9927B2??78?7:359B5932B3?;B903?AB?BA
AB?BA
1;2
1; 7AB58?94=9B:3A77A3?30BA
5
793A6B7 3?;B913;0B5
K
3?;B9139B5 ,AB9;3567AB58?94=9B:3A772A275B93?;03?79BA
K K
K
1; 278?94=9B:3
1;
Contoh
6.12
Gambar 6.38
Lensa tipis a bikonveks, R
1
0 ; R
2
b konvek konkaf, R
1
0 ; R
2
c plan konveks, R
1
= ; R
2
d bikonkaf, R
1
0 ; R
2
e konkaf konveks, R
1
0 ; R
2
f plan konkaf, R
1
= ; R
2
.2302
3A772:6:3E5;3;7:79793A30:8B6:30769317: 2702759 235 27;3A3? 93:359B5E 3 A77 2A
27:;05923530B65?7 2-1 27AB8B99 0303?837:3A77
:;:3A7703?:9B3?;03?79BA K
b a
c
R
1
R
1
R
2
R
2
e d
f
R
1
R
2
R
1
R
2
R
1
R
2
R
1
R
2
c. Perbesaran Bayangan Lensa
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