Radio radiation

Almost a millennium ago, humans stared in wonder at a new star. Today, there is a pulsar, seemingly beaming pulses of radio radiation to us at precise intervals, and a of gas surrounding it. What has happened ... 

The radiation does not fall in the visible region it is radio radiation. (See Figure 7.4 of the text.)... 

Microwave radiations are electromagnetic radiations. Their frequencies, wavelengths and energies lie between that of infrared (IR) and radio radiations. Here, radiation means rays and not the radioactive irradiatioa Let ns compare the three ... 

Electromagnetic radiation (Section 13 1) Vanous forms of ra diation propagated at the speed of light Electromagnetic radiation includes (among others) visible light infrared ul traviolet and microwave radiation and radio waves cos mic rays and X rays... 

Colorimetry, in which a sample absorbs visible light, is one example of a spectroscopic method of analysis. At the end of the nineteenth century, spectroscopy was limited to the absorption, emission, and scattering of visible, ultraviolet, and infrared electromagnetic radiation. During the twentieth century, spectroscopy has been extended to include other forms of electromagnetic radiation (photon spectroscopy), such as X-rays, microwaves, and radio waves, as well as energetic particles (particle spectroscopy), such as electrons and ions. ... 

If energy of the proper frequency is supplied, a transition between these quantum states occurs with the absorption of an amount of energy equal to the separation of the states. The frequency of the absorbed radiation lies in the radio-frequency range and depends on the local magnetic field at the atom in question. 

Spectroscopy is basically an experimental subject and is concerned with the absorption, emission or scattering of electromagnetic radiation by atoms or molecules. As we shall see in Chapter 3, electromagnetic radiation covers a wide wavelength range, from radio waves to y-rays, and the atoms or molecules may be in the gas, liquid or solid phase or, of great importance in surface chemistry, adsorbed on a solid surface. 

A unique process for chemical stabili2ation of a ceUular elastomer upon extmsion has been shown for ethylene—propylene mbber the expanded mbber obtained by extmsion is exposed to high energy radiation to cross-link or vulcani2e the mbber and give dimensional stabUity (9). EPDM is also made continuously through extmsion and a combination of hot air and microwaves or radio frequency waves which both activate the blow and accelerate the cure. 

Frequency Allocations. Under ideal conditions, an optimum frequency or frequency band should be selected for each appHcation of microwave power. Historically, however, development of the radio spectmm has been predominantly for communications and information processing purposes, eg, radar or radio location. Thus within each country and to some degree through international agreements, a complex Hst of frequency allocations and regulations on permitted radiated or conducted signals has been generated. Frequency allocations developed later on a much smaller scale for industrial, scientific, and medical (ISM) appHcations. 

The frequency of microwave radiation lies between that of IR radiation and high frequency radio waves and the boundaries between these regions are not fixed [221]. The microwaves are generated in a transmitter (magnetron) which possesses a stalk which penetrates Uke a radio antenna into a hollow energy guide (Fig. 48). This leads the electromagnetic waves into the reaction chamber (power about... 

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