Proteins and amino acids that contain phenyl rings form a yellow colored compound when treated with concentrated nitric acid. The yellow stains on the skin are caused due to the reaction of nitric acid with protein keratin present in the skin. This reaction is called xanthoproteic reaction
Ultraviolet Light has the highest frequency between the three, Visible Light would stay in the middle since its in the middle of the spectrum, thus making Infrared the lowest.
