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The ratio varies from 0 to 1. The surface of a perfect black body (with an emissivity of 1) emits thermal radiation at the rate of approximately 448 watts per square metre (W/m 2) at a room temperature of 25 °C (298 K; 77 °F). Objects have emissivities less than 1.0, and emit radiation at correspondingly lower rates. [1]
In ice cores, mainly Arctic and Antarctic, the ratio of 18 O to 16 O (known as δ 18 O) can be used to determine the temperature of precipitation through time.Assuming that atmospheric circulation and elevation has not changed significantly over the poles, the temperature of ice formation can be calculated as equilibrium fractionation between phases of water that is known for different ...
In the case of global energy flux, the W/m 2 value is obtained by dividing the total energy flow over the surface of the globe (measured in watts) by the surface area of the Earth, 5.1 × 10 14 m 2 (5.1 × 10 8 km 2; 2.0 × 10 8 sq mi). [3]
The radio window is the region of the radio spectrum that penetrate the Earth's atmosphere. Typically, the lower limit of the radio window's range has a value of about 10 MHz (λ ≈ 30 m); the best upper limit achievable from optimal terrestrial observation sites is equal to approximately 1 THz (λ ≈ 0.3 mm). [1] [2]
Since the radiation of the dipole is concentrated in horizontal directions, the gain of a half-wave dipole is greater than that of an isotropic antenna. The isotropic gain of a half-wave dipole is 1.64, or in decibels 10 log 10 ( 1.64 ) = 2.15 d B , {\displaystyle \ 10\ \log _{10}(1.64)=2.15\ {\mathsf {dB}}\ ,} so G i = 1.64 G d ...
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency [1] range from around 20 kHz to around 300 GHz.
the blackbody spectrum of sunlight coming into the Earth's atmosphere, Rayleigh scattering of that light off oxygen and nitrogen molecules, and; the response of the human visual system. The strong wavelength dependence of the Rayleigh scattering (~λ −4) means that shorter wavelengths are scattered more strongly than longer wavelengths. This ...
Oxygen in Earth's air is 99.759% 16 O, 0.037% 17 O and 0.204% 18 O. [13] Water molecules with a lighter isotope are slightly more likely to evaporate and less likely to fall as precipitation, [14] so Earth's freshwater and polar ice have slightly less (0.1981%) 18 O than air (0.204%) or seawater (0.1995%).