Light sources. Shadow

Light is radiation that causes the sensation of sight. Bodies that emit light themselves are called light sources. Natural sources: the Sun and other stars, lightning, fire, fireflies, some deep-sea animals. Artificial sources: incandescent, fluorescent and LED lamps, a candle, a torch, a laser. The Moon, the planets, a book and a table do not emit light themselves: we see them because sunlight or lamplight is reflected from them — they are illuminated bodies. Devices that receive light: the eye (a living receiver), a camera, a solar cell, plant leaves (for photosynthesis). Light carries energy: a solar cell turns it into electrical energy, a plant into chemical energy, a black surface into heat. We see when light enters the eye: for seeing, light either from the source itself or reflected from a body must enter the eye. Protect your eyes: do not look straight at the Sun, do not stare at a very bright laser or lamp, and read in good light.