Violet light has the most energy per photon of any visible color of light with a wavelength of about 400 nm. Ultraviolet light has an even smaller wavelength and as a result, more energy per photon, but it is invisible to the human eye.
The spectrum of visible light runs from violet to red. It is banded on either side by ultraviolet and infrared, colors which human beings cannot perceive unassisted. Red light has the longest wavelength with about 650 nm. There are many other colors which human beings cannot perceive but which are measurable through instrumentation.
Other colors of the spectrum and their wavelengths include:
- Orange light with a wavelength of roughly 590 nm.
- Yellow light with a wavelength of roughly 570 nm.
- Blue light with a wavelength of roughly 475 nm.
Different wavelengths of light scatter differently through varying mediums, most noticeably Earth's atmosphere. The sky appears blue both because the sun releases a great deal of blue light and because blue light scatters upon contact with Earth's atmosphere, diffusing through it and influencing human perception heavily.
Ultraviolet light is so powerful that it can cause sunburns by destroying and breaking down cellular structures. This is its most visible impact on daily human life and the most easily measured by its perceivable influences.