FREQUENCY AND WAVELENGTH

EM waves travel through space at the speed of light, which is approximately 2.99792 × 10⁸ m/s (1.86262 × 10⁵ mi/s). This is often rounded up to 3.00 × 10⁸ m/s, expressed to three significant figures. The wavelength of an EM field in free space gets shorter as the frequency becomes higher. At 1 kHz, the wavelength is about 300 km. At 1 MHz, the wavelength is about 300 m. At 1 GHz, the wavelength is about 300 mm. At 1 THz, an EM signal has a wavelength of 0.3 mm—so small that you would need a magnifying glass to see it.
The frequency of an EM wave can get much higher than 1 THz; some of the most energetic known rays have wavelengths of 0.00001 Ångström (10^-5 Å). The Ångström is equivalent to 10^-10 m and is used by some scientists to denote extremely short EM wavelengths. A microscope of great magnifying power would be needed to see an object with a length of 1 Å. Another unit, increasingly preferred by scientists these days, is the nanometer (nm), where 1 nm = 10^-9 m = 10 Å. The formula for wavelength λ, in meters, as a function of the frequency f, in hertz, for an EM field in free space is
λ = 2.99792 × 10⁸/f
This same formula can be used for λ in millimeters and f in kilohertz, for λ in micrometers and f in megahertz, and for λ in nanometers and f in gigahertz. Remember your prefix multipliers: 1 millimeter (1 mm) is 10^-3 m, 1 micrometer (1 μm) is 10^-6 m, and 1 nanometer (1 nm) is 10^-9 m. The formula for frequency f, in hertz, as a function of the wavelength λ, in meters, for an EM field in free space is given by transposing f and λ in the preceding formula:
f = 2.99792 × 10⁸/λ
As in the preceding case, this formula will work for f in kilohertz and λ in millimeters, for f in megahertz and λ in micrometers, and for f in gigahertz and λ in nanometers.