The most accurate concept of light source "Look at physics professors"

Light sources can be divided into three types. The first is the light produced by thermal effect. Sunlight is a good example. Besides, candles and other items are the same. This light will change color with the change of temperature. The second is atomic luminescence. The fluorescent substance coated on the inner wall of fluorescent tube is excited by electromagnetic wave energy to produce light, and the principle of neon lamp is the same. Atomic luminescence has its own basic color. The third is the synchrotron, which emits powerful light. This is the light from the atomic furnace, but we rarely have the opportunity to come into contact with this light in our daily life.

Objects that emit light by reflection, scattering, transmission and refraction are not light sources, so we should understand the definition of light source from the generation of light.