Wednesday, June 6, 2012

Hukum Pembiasan Gelombang Cahaya

Pembiasan adalah peristiwa pembelokan arah rambat gelombang akibat melewati bidang batas dua medium yang berbeda.  Cahaya sebagai gelombang  mengalami pembiasan ketika melewati bidang batas dua medium yang berbeda misalnya ketika cahaya berasal dari udara menuju ke air maka arah siar akan dibelokkan. Kali ini blogger akan membahas hukum pembiasan gelombang cahaya.

Cahaya sebagai gelombang elektromagnetik  melewati sifat sama seperti gelombang.  Hukum pembiasan secara umum juga akan berlaku sama untuk gelombang cahaya.

Hukum utama pembiasan

Hukun I pembiasan dari Snellius : sinar datang, sinar bias dan garis normal terletak pada satu bidang datar.

pembiasan cahaya
Sudut datang (i) adalah sudut yang dibentuk antara sinar datang dengan garis normal dan sudut bias adalah sudut yang dibentuk antara sinar bias  dengan garis normal

Indeks bias

Indeks bias mutlak,

Indeks bias mutlak adalah suatu ukuran kemampuan medium itu untuk membelokkan cahaya. Jadi tipa medium akan memiliki indeks bias yang berbeda indeks bias mutlak juga menunjukkan kerapatan dan kerenggangan suatu bahan misalnya gelas lebih rapat dari pada air maka indeks bias gelas lebih besar dari pada air.
dimana n= indeks bias mutlak, i= sudut datang, dan r= sudut bias

Indeks bias relatif

Adalah ukuran perbadingan indeks bias madium satu terhadap medium lainnya. Secara umum ditulis dalam sebuah persamaan n1 sin i = n2 sin r dimana n1 = indeks bias mutlak medium 1, n2= indeks bias mutlak medium 2, i= sudut datang dan r =- sudut bias.
Dalam persamaan berikut    
disebut indeks bias medium 2 relatif terhadap medium satu dengan cara yang sama 
disebut indeks bias medium 1 relatif terhadap medium 2

Hukum II pembiasan Snellius

Hukum kedua Snellius berbunyi: sinar datang dari medium kurang rapat ke medium lebih rapat (n1 < n2) , sinar akan dibelokkan mendekati garis normal. Jika sinar datang dari medium lebih rapat ke medium kurang rapat (n1 > n2). Sinar akan dibelokkan menjauhi garis normal.


Gambar yang pertama sebelah kiri adalah cahaya dibelokkan mendekati garis normal dan yang sebelah kanan cahaya di belokan menjauhi garis normal.


  1. keren banget, penjelasannya..!! :-)

  2. jadi inget waktu sekolah dulu pas waktu ujian di tes per-orang untuk menjelaskan mengapa pensil di dalam air gelas bisa terlihat bengkok ..
    Waktu itu saya pusing sekali tapi syukur semuanya dapat di atasi

  3. Makasih Atas penjelasan smua.nya.. :D

  4. ini sih pelajaran yang susah gan, pas waktu smp dlu ?

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