Caption: Examples of electromagnetic radiation (EMR) wavelength to frequency conversion for the visible light band (fiducial range 0.4--0.7 μm).
Note that though you often give visible light wavelength in the units angstrom (Å) = 0.1 nm = 10**(-10) m, nanometer (nm) = 10**(-9) m, or micron (μm) = 10**(-6) m, you usually convert to meters in order to calculate frequency since those are the standard metric units for calculations.
For example:
λ = 400 nm = 400 x 10**(-9) m ,and so
f = c/λ ≅
= 3 x 10**8 /( 4 x 10**(-7) )
= 7.5 x 10**14 Hz ,
where we use the familiar
phase velocity formula fλ=c
and
the
vacuum light speed c = 2.99792458*10**8 m/s ≅ 3*10**8 m/s ≅ 1 ft/ns.
Credit/Permission: ©
David Jeffery,
2003 / Own work.EOF
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