Since light is a wave, like all other waves it must have a wavelength and an amplitude. Wavelength and frequency determine the color of the light, amplitude affects the brightness.

The relationship between energy and frequency is

E = hn

(ie energy, E and frequency, n are directly proportional)

The relationship between wavelength and frequency is

c = nl

(ie the speed of light, c, which is constant, means that wavelength, l and frequency are inversely proportional. When one increases, the other decreases)

Combing these we get:

E = h c / l

which shows that as wavelength gets longer, the energy of the light decreases (becomes more red-like) Red light has the lowest amount of energy of the visible region, and violet light has the most energy.

Wavelength, lmax (nm)
Color absorbed
Color observed
380-420
violet
green-yellow
420-440
violet-blue
yellow
440-470
blue
orange
470-500
blue-green
red
500-520
green
purple
520-550
yellow-green
violet
550-580
yellow
violet-blue
580-620
orange
blue
620-680
red
purple
680-780
purple
green