Electromagnetism early experiments

Although many of the early experiments in microwave-assisted organic synthesis have been carried out in domestic microwave ovens, the current trend clearly is to use specialized instruments for this type of chemical synthesis. Experiments carried out in domestic ovens have been found to be difficult to reproduce, owing to the lack of temperature and pressure control, pulsed irradiation, uneven electromagnetic field distributions, and the unpredictable formation of hotspots. 

The electrical age was built on the discovery in the early 1830s, independently by Joseph Henry (1797-1878) in America and Michael Faraday (1791-1867) in England, of electromagnetic induction, which led directly to the invention of the dynamo to generate electricity from steam-powered rotation. It came to fruition on New Year s Eve, 1879, when Thomas Edison (1847-1931) in rural New Jersey, after systematic and exhaustive experiments, made the first successful incandescent lamp, employing a carbonised filament made from some thread taken from Mrs. Edison s sewing cabinet. The lamp burned undimmed for 40 h, watched anxiously by Edison and some of his numerous collaborators. This lamp was ideal for... 

Spectrometer — Spectrometers are instruments to record spectra, i.e., intensity (or absorbance) versus wavelength or versus frequency of electromagnetic radiation. The interaction of matter with electromagnetic radiation can be studied in absorption or in emission mode. In the former case electromagnetic radiation (used as probe) is interacting with matter. (The term spectroscope refers to the early instruments where the spectra were observed with the eye. Although in all modern experiments the spectra are measured and recorded, the term spectroscope is still used synonymously to spectrometer.)... 

Influenced hy the electromagnetic theoretical prediction that oscillating electric charges would emit radiation, which was demonstrated when Heinrich Hertz experimented with emitted long-wavelength radiation, prominent physicists of the late nineteenth and early twentieth centuries pursued the idea that the oscillation... 

Later (after Maxwell s death at an early age) his conclusion was confirmed experimentally by Heinrich Hertz, who showed that a spark from two charged spheres sets up an electromagnetic wave that can trigger a spark in similar charged spheres a distance away (which eventually became the basis for radio technology). But then Hertz took his experiment one step further. He showed that the spark came easier when ultraviolet light was shining on the spheres. He did not have an explanation for this observation at the time, but we soon will have. 

Two important developments in the early history of radioactivity were (1) the recognition of the three different types of radiation, a, P, and y rays, distinguished by their very different penetration in matter and (2) the realization that in each of the three decay series there existed a product that behaved chemically like an inert (also called rare or noble) gas. Through experiments involving deflection in magnetic and electric fields, a and P rays were soon identified as streams of helium ions and electrons, respectively, and y rays, undeflected by such fields, were recognized as a form of electromagnetic radiation akin to X-rays. 

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