Supiyanto Kelas X Evaluasi Bab 5 Nomor 9

Titik dekat mata seseorang 200 cm de depan mata. Agar orang itu dapat melihat benda pada jarak 25 cm, maka perlu menggunakan kacamata berkekuatan …

Penyelesaian

Fokus lensa

$\frac{1}{f}=\frac{1}{25}-\frac{1}{200}$

$\frac{1}{f}=\frac{7}{200}\frac{1}{\text{cm}}$

Daya lensa

$P=100\times \frac{7}{200}=3,5~\text{D}$

Jawaban B

Supiyanto. 2006. FISIKA UNTUK SMA KELAS X. Jakarta: Phiβeta.

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