Energy, Frequency, and Wavelength

A wave can be characterized by its wavelength, but we can also characterize it by the frequency (how many wavelengths pass a fixed point in a given time) and the energy that it carries. For light waves the relationship among the wavelength (usually denoted by Greek "lambda"), the frequency (usually denoted by Greek "nu"), and the energy E are


where c is the speed of light and h is another universal constant called Planck's Constant that has the values

h = 4.135 x 10 -15 eV-sec = 6.625 x 10 -27 erg-sec

in two different useful sets of units (eV stands for "electron volts"; electron volts and ergs are two common units of energy). Thus, these equations allow us to freely interconvert among frequency, wavelength, and energy for electromagnetic waves: specifying one also specifies the others.