Microwave, wavelength

The neutrino Sun never sets. Sixty billion neutrinos blasted out from the Sun s core eight minutes ago fly through every square centimetre of our body each second. We feel absolutely nothing and neither do they. They are the height of discretion. The night is not absolutely dark because, not only are we forever bathed in the cosmic background radiation at microwave wavelengths, but we... 

A transparent Universe. After 300,000 yr temperatures dropped to 4,500 K and gave rise to the formation of atomic matter, and atoms of hydrogen, helium, and deuterium were formed. Because electrons were removed from the plasma through the formation of atoms, radiation streamed out and the Universe became transparent. Initially the Universe contained abundant ultraviolet-and X-rays, now cooled down to microwave wavelengths. This is what is recorded as the Cosmic Background radiation. 

Absolute permittivity of vacuum (8.854pF m ) Free space microwave wavelength Magnetic constant (1.26 pH m )... 

K (top panel) however, the v = 1 line (bottom panel) shows much stronger emission near 9 K and a narrower line profile. These transitions were observed to illustrate maser emission in space. (A maser is a laser at microwave wavelengths.) The 7= 2 1 transition in v = 1 is pumped by infrared radiation... 

Hence, the microwave wavelength varies between 1 m and 1 mm as the frequency increases. Each frequency range is referred to by its band designation as listed in Table 1. The microwave power (P) transmitted per unit area is given by Poynting s Vector as... 

Microwave radiometer is a device which measures the intensity of electromagnetic radiation from human body in microwave wavelength. The noise power at the input of the microwave reeeiver is proportional to the internal temperature of the human body. An array of receivers can resolve the local temperature inside the breast in 3-D and... 

Microwave Heating. Microwaves (wavelength of 3 to 30 cm) are used to heat foods as a result of molecular excitation of food and their penetration power. Microwave heated foods do not have a heat gradient. Foods containing high moisture and fat readily absorb microwaves and are cooked or baked. Application of microwave for both home and institutional meal preparation has increased because of its convenience and rapid heating when compared to conventional means. 

Knitting electrically conductive fibres can introduce some highly sophisticated functionality. For example, a paper by Tennant et al. (2012) describes methods for producing frequency-selective surfaces at microwave wavelengths. This was achieved using silver-coated nylon yam on a polyester base. Alternatively, knitted conductive yams can be used to create touch sensor switches (Wijesiriwardana et al., 2005) or knitted strain sensors for stroke rehabilitation (Preece et al., 2011). 

One of the most fruitful application of laboratory microwave spectroscopy over the last twenty years is the analysis of the molecular content of interstellar clouds. These clouds contain gas (99% in mass) which has been mostly studied by radioastronomy, and dust, whose content has been analysed mostly by IR astronomy. The clouds rich in molecular content are dense or dark clouds (they present a large visual extinction), with a gas density of 10 -10 molecules cm", and temperatures of T < 50K. At these low temperatures only the low-lying quantum states of molecules can be thermally (or collisionally) excited, i.e. rotational levels. Spontaneous emission from these excited states occurs at microwave wavelengths. In some warm regions of dense clouds (star formation cores) the absorption of IR radiation produces rotational emission in excited vibrational states. Other rich chemical sources are the molecular clouds surrounding evolved old stars, such as IRC-i-10216, and called circumstellar clouds. 

---