Light source refers to the self brightness of an object, also known as the self brightness of an object. Some objects in the universe emit light, while others do not. We refer to objects that can emit light on their own and are emitting light as light sources. The sun, turned on electric lights, burning candles, etc. are all light sources. In physics, it refers to an object that can emit electromagnetic waves within a certain wavelength range (including visible light and ultraviolet, infrared, X-ray, and other invisible light). Usually refers to a luminescent substance that emits visible light. Any object that can emit light itself is called a light source, also known as a luminous body. Such as the sun, stars, lamps, and burning substances. But things like the surface of the moon, tabletops, white paper, paper books, etc. rely on them to reflect external light in order for people to see them. Such reflective objects cannot be called light sources, which are also known as bright and cannot be called light sources. This is called bright when illuminated and cannot be called light sources because it is not self illuminating or self illuminating. Visible light sources are indispensable in our daily lives. Visible and invisible light sources are also widely used in industries, agriculture, medicine, and modernization of national defense. The object that is emitting light is called a light source. Light sources can be divided into natural (natural) light sources and artificial light sources. In addition, according to the direction of light propagation, light sources can be divided into point light sources and parallel light sources