Radiation radiowaves

LIDAR is an acronym for light detection and ranging . The technique uses the same principles as RADAR, an acronym for radiowave detection and ranging . RADAR is used for measuring the distance of an object from an observer. The time taken for radiowave radiation to travel to and from the object, which reflects or backscatters the radiation, is readily translated into a measurement of distance. 

Double-resonance spectroscopy involves the use of two different sources of radiation. In the context of EPR, these usually are a microwave and a radiowave or (less common) a microwave and another microwave. The two combinations were originally called ENDOR (electron nuclear double resonance) and ELDOR (electron electron double resonance), but the development of many variations on this theme has led to a wide spectrum of derived techniques and associated acronyms, such as ESEEM (electron spin echo envelope modulation), which is a pulsed variant of ENDOR, or DEER (double electron electron spin resonance), which is a pulsed variant of ELDOR. The basic principle involves the saturation (partially or wholly) of an EPR absorption and the subsequent transfer of spin energy to a different absorption by means of the second radiation, leading to the detection of the difference signal. The requirement of saturability implies operation at close to liquid helium, or even lower, temperatures, which, combined with long experimentation times, produces a... 

In the microwave and radiowave regions, virtually monochromatic incident radiation is generated and the need for a monochromator is thus obviated. 

Radiations outside the ultraviolet, visible and infrared regions cannot be detected by conventional photoelectric devices. X-rays and y-rays are detected by gas ionization, solid-state ionization, or scintillation effects in crystals. Non-dispersive scintillation or solid-state detectors combine the functions of monochromator and detector by generating signals which are proportional in size to the energy of the incident radiation. These signals are converted into electrical pulses of directly proportional sizes and thence processed to produce a spectrum. For radiowaves and microwaves, the radiation is essentially monochromatic, and detection is by a radio receiver tuned to the source frequency or by a crystal detector. 

Controlled radiation sources provide the most important modem tools for studying molecular structure and chemical dynamics. Virtually everything we know about the ways atoms interact has been deduced or confirmed by irradiation at a wide variety of wavelengths, from radiowaves to X-rays. In fact, protein and DNA structural determinations were the most important driving force in creating the modem chemical and molecular basis for the biological sciences. 

Various Types of Electromagnetic Radiations The various types of electromagnetic radiations are radiowaves, microwaves, infrared waves, ultraviolet waves, visible light, X-rays, g-rays, cosmic rays, etc. 

Solvents used in ultraviolet, visible, infrared, microwave, and radiowave spectroscopy must meet the following requirements transparency and stability toward the radiation used, solubility and chemical stability of the substance to be examined, and a high and reproducible purity ( optical constancy ). Normally, intermolecular interaction with the solute should be minimal. On the other hand, important information about the solute can be obtained from the changes in the absorption spectrum arising from such interactions. 

The present state of knowledge about invisible dark matter indicates that it represents the predominant part (about 90%) of the total mass of the universe. It includes the so-called missing mass. Dark matter is not discernible by any kind of electromagnetic radiation in the region from y rays to radiowaves, but its gravitational effects on other kinds of matter are observable. For example, the rotation of spiral galaxies such as the Milky Way can only be explained if 90% of the matter is invisible in the sense mentioned above. The question of the nature of the dark mass is still open. Various possibilities are discussed matter different from that on the earth (no protons, neutrons and electrons), remnants of the big bang, neutrinos. However, the actual mass of neutrinos is still uncertain. 

Microwaves (0.3-300 GHz) lie between radiowave (RF) and infrared (IR) frequencies in the electromagnetic radiation spectrum. Microwaves can be reflected, absorbed and/or transmitted by materials. Microwaves can interact with materials through either polarization or conduction processes. Polarization involves the short-range displacement of charge through... 

Indeed, it was Maxwell s generalization of the laws of electrodynamics that revealed that the radiation solutions of these equations, which would not have appeared in the earlier version (without the displacement current term) predicted all the known optical phenomena. After Maxwell s investigation of these optical implications of electrodynamics, other portions of the spectrum of radiation solutions were predicted and discovered empirically radiowaves, X- rays, infrared radiation, and gamma rays. Thus, it was Maxwell s intuitive feeling for the need of symmetry in his laws of electrodynamics that led to the full unification of electrodynamics and optics in the expression of Maxwell s equations. 

---