Light of different colors has wavelengths of different lengths. The shorter the wavelength, the farther the light travels to the four sides.
The wavelength of the yellow light is much shorter than the white light emitted by the big light. The distance of the illumination is much farther and the penetration is much stronger. Therefore, when there is fog, the car turns on the yellow fog light instead of the headlights. Lighting, this is a good way to make full use of the characteristics of different colors of light and to avoid weaknesses.
Yellow light can also be used as a warning sign. Late at night, over the intersection of the city, a yellow light hangs high. Even in the foggy night, yellow light can be seen far away to remind the driver to pass safely through the intersection. In fact, the light source in the yellow light is still emitted by an ordinary white light bulb, but the color of the light-transmissive glass on the lampshade is yellow. After the white light passes through the yellow glass, it turns into yellow light.