Spectrum of Electromagnetic Radiation

The full electromagnetic spectrum spans an enormous range of wavelengths, and the narrow band of visible light plants rely on is only its smallest slice - yet the entire living world depends on that slice as its driving energy source. Of the total solar radiation reaching Earth, wavelengths span roughly 300 to 2600 nm, while the visible portion within that - the part the human eye (and plant pigments) can detect - spans only about 390 to 763 nm (3900 to 7630 Angstrom). The colour of light is set entirely by its wavelength, and the energy carried by a quantum of light is inversely proportional to its wavelength, meaning shorter-wavelength light (such as blue or violet) carries more energy per photon than longer-wavelength light (such as red). Ranked from shortest to longest wavelength, the full electromagnetic spectrum consists of eight bands: cosmic rays, gamma rays, X-rays, ultraviolet rays, the visible light spectrum, infrared rays, longer electric-type rays, and finally radio rays. Light itself has several defining physical properties: it is a transverse electromagnetic wave, made up of an oscillating electric field and an oscillating magnetic field that are perpendicular to each other and both perpendicular to the direction the light is travelling; it moves at a constant speed of $3 \times 10^8$ m/s; its wavelength is the distance measured between two successive wave crests; and, treated as a particle rather than a wave, light exists as discrete photons, each photon carrying a fixed packet of energy called a quantum, with a phot …