Units for Electromagnetic Spectrum

Wavelength, l, - visible Region- approx. 350 nm to 700 nm (nm = nanometres).

 
Energy increases towards shorter wavelength, towards ultraviolet.

 E = hn = hc/l

h = Planck�s constant = 6.626196 x 10-27 erg sec

c = speed of light = 2.9979 x 1010 m s-1

 We commonly use 1/l as a unit of energy, so-called inverse cm, or cm-1  or wqvenumbers.

 Visible region is from about 14,300 cm-1 (red) to 28,600 cm-1 (blue).

 or in electron volts: (eV)

red 1.77, to blue 3.55 eV

 
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