4. Refraction of light at curved surfaces

When light travels from one transparent medium to another—such as air to water or air to glass—its path changes direction. This bending of light is called refraction. It happens because the speed of light changes in different media. Due to refraction, objects under water appear shifted or raised, which is why a stick partly dipped in water seems bent.

Understanding refraction helps us explain many natural and technological phenomena. It is the principle behind lenses, spectacles, microscopes, telescopes, and cameras. By studying refraction, students learn how light travels through different materials and how it helps us see clearly, correct vision problems, and design powerful optical instruments used in science and daily life. 🔍