Question

Eye is more sensitive to yellow color. Why are then danger signals red?

Answer 1

The scattering (Rayleigh scattering) of light is inversely proportional to the fourth power of the wavelength of light. So, the scattering of red light is much less than the yellow light and accordingly, the red light signals can be seen up-to a longer distance without much loss in their intensity. For this reason, the danger signals are red in color.