The two basic quantities which describe a light wave are the frequency
f, of the wave (usually given in hertz, HZ, or cycles per second), and
the wavelength, 
. These quantities are related to each other and
to the speed of light c, by:
If you know the wavelength of light, you can find the frequency and
vice versa. For example if 
Hz, the wavelength 
In some problems the frequency will be given in a unit like MHz
(mega-hertz). 1.0 MHz = 
Hz. In other problems, the wavelength
will be given in nano-meters (nm). 1.0 nm = 
m.
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