Refraksi
caption: Refraksi (pembiasan) gelombang-gelombang cahya ing toya. Persegi gelap nedahaken posisi ingkang sajatosipun sebatang pensil ingkang manggèn ing semangkuk toya. Persegi terang nedahaken posisi punika saking pensil punika. Perhatikan bahwa ujungnya (X) seakan-akan terlihat di Y, posisi ingkang langkung gamblang dangkal.
caption: Sedotanipun katingal ceklek amargi refraksi cahya ingkang nongol saking toya menuju dateng hawa.
caption: A calcite crystal laid upon a paper with some letters showing the double refraction
caption: A gradient-index lens with a parabolic variation of refractive index ( n ) with radial distance ( x ). The lens focuses light in the same way as a conventional lens.