The physical nature of light is explained by physicists as an emission of subatomic particles called photons by other particles called electrons. Light also has wave properties that allow for different frequencies. Light travels at a velocity of about 186,282 miles per second. Currently there is nothing in the known universe that travels faster than light.
The psychological nature of light is the result of the brain processing signals from photoreceptor cells in our eyes. Normal human photoreceptor cells detect only the red, blue and green wavelengths of light. Consequently, all the colors we see are the result of the way these signals are combined and processed. In other words, our perception of yellow light is an illusion created by the brain when higher intensity red and green wavelengths are detected at the same time. This type of vision is called trichromatic color vision.