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.

مواضيع ذات صلة

أصول عدم الانعكاس

الانعكاس يولد الانعكاس

الاحتمالية في الميكانيكا الإحصائية

القابلية للانعكاس وعدم القابلية للانعكاس

نظرة في تعددية الفيزياء

الاختزال وعدم القابلية للانعكاس

الواقعية العلمية وتغيير النظريات

نقص الإثبات ومذهب الذرائعية ومذهب الواقعية

مشكلة التمييز: متى يكون المنهج علميا؟

المنهج العلمي: من الاستقراء إلى التكذيب وما بعده

مناهج العلوم وثمارها

!Parity is not conserved