Waves A Wave is any periodic fluctuation traveling through a medium that carries energy. Speed depends on water depth, salinity, etc. Light as electromagnetic waves Can treat light as an Electromagnetic Wave Fluctuation in the intensity of electric and magnetic fields. Travels through a vacuum at the speed of light. The wavelengths given in the table above are only approximate.
Color is a physiological response of our brains to light of different wavelengths.
I include approximate wavelengths primarily for purposes of illustration. It did not enter the language until the Middle Ages, when the fruit of the same name reached Europe from the Middle East. Massless particle that carries energy at the speed of light. Demonstrating this won Einstein the Nobel Prize. We need a way to quantify how bright an object is.