Light & Optics

How light travels, reflects, and bends

Light travels in straight lines called rays. When light hits a smooth surface (like a mirror), it bounces off — this is reflection. The angle at which light hits equals the angle at which it bounces: angle of incidence = angle of reflection. When light passes from one material to another (air to water, for example), it bends — this is refraction. Light bends toward the normal line when entering a denser medium and away when leaving. This is why a straw looks bent in a glass of water. Objects appear a certain color because they reflect that color of light and absorb all others. Transparent objects let light through; opaque objects block it; translucent objects let some through.