• 1 · Religion and Magic
• 2 · Nature
• 3 · Human Being, Man in General
• 4 · Society, Civilization, Culture
• 5 · Abstract Ideas and Concepts
• 6 · History
• 7 · Bible
• 8 · Literature
• 9 · Classical Mythology and Ancient History

• Top
• 4 · Society, Civilization, Culture
• 49 · education, science and learning
• 49E · science and technology
• 49E2 · physics and mechanics
• 49E25 · optics

49E252 · refraction (optics)