question_answer

Eye is more sensitive to yellow colour. Why do then we use traffic light stop signals of red colour?

Answer:

                According to Rayleigh's law of scattering, the intensity of light of wavelength \[\lambda \] present in the scattered light is inversely proportional to fourth power of wavelength \[\lambda \] : \[I\propto \frac{1}{{{\lambda }^{4}}}\] In the visible spectrum, red colour has the largest wavelength, it is least scattered and can be easily observed even in foggy and dust conditions.