List the colors of the visible spectrum in order of decreasing energy.

Question

List the colors of the visible spectrum in order of decreasing energy.

Answer 1

violet     - 380–450 nm

blue       - 450–495 nm

green    - 495–570 nm

yellow   - 570–590 nm

orange - 590–620 nm

red        - 620–750 nm

The visible spectrum (or sometimes called the optical spectrum) is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths in air from about 380 to 750 nm. The corresponding wavelengths in water and other media are reduced by a factor equal to the refractive index. In terms of frequency, this corresponds to a band in the vicinity of 400–790 terahertz. A light-adapted eye generally has its maximum sensitivity at around 555 nm (540 THz), in the green region of the optical spectrum. The spectrum does not, however, contain all the colors that the human eyes and brain can distinguish. Unsaturated colors such as pink, and purple colors such as magenta are absent, for example, because they can only be made by a mix of multiple wavelengths.

Answer 2

Light can be thought of as consisting of photons, for this purpose. The energy of a photon is Planck's constant times frequency.

As you probably know, in the spectrum's colors, red has the longest wavelength and violet the shortest.

Since the speed of light is a constant, and the speed is frequency times wavelength, the frequency of violet must be the highest and that of red the lowest.

Therefore, from our equation of energy, violet has the highest energy and red the lowest.