On rainy days, we will find that the street lamps in the rain have rings of light, which comes from the dispersion of light. On rainy days, the air is filled with countless small water droplets, each of which is like a Newton prism. The wavelength of the light emitted by the street lamp is not single, and the refraction angles of light with different wavelengths (colors) are different in the small water droplets. Because these lights are dispersed when passing through the small water droplets around the street lamp, the light of different colors is separated. The small water droplets are evenly covered in the air, so when the street lamp is on, the light refracts in these small water droplets and forms a circle of halo around it. Dispersion also occurs when light touches tiny ice particles. Therefore, in the cold winter, when the air is full of tiny ice particles, a beautiful halo will appear around the lit street lamps.