Читать книгу Quantum Physics is not Weird. On the Contrary. - Paul J. van Leeuwen - Страница 23

In 1886, seven years after Maxwell's publication, Heinrich Hertz (1857-1894) confirmed the existence of standing electromagnetic (radio) waves with a wavelength of almost 61 meters (200 ft). It is probably not a coincidence that the depth of his laboratory was 30 meters, so that half that wavelength did fit precisely. Maxwell's theory was confirmed. Hertz saw no practical use for his discovery. Guglielmo Marconi (1874-1937) saw its application potential and realized the first radio communication in 1889. In 1896, shortly after that, the telegram service and the Morse code were invented. Nikola Tesla (1856-1943) forgot to patent his invention concerning sound communication using radio waves and the cunning Marconi received also the credits for that.

In 1895, Wilhelm Röntgen (1845-1923) discovered highly energetic EM-waves he generated by applying a high voltage between the electrodes of a vacuum tube. Röntgen called his discovery X-rays.

Figure 3.10: Albert von Kölliker's hand photographed by Röntgen.

These X-rays have wavelengths between 0.01 and 10 nanometers. The first X-ray photos are those of Röntgen's acquaintances, see figure 3.10 for an X-ray of Albert von Kölliker's hand. Röntgen also took such an X-ray of his wife's hand. Upon seeing the result, she feared her end was near. It is incidentally remarkable that Röntgen made his discovery because he noticed that a screen covered with barium platinocyanide lit up in his darkened laboratory when he switched his vacuum device on. The fact that he had such a screen accidentally standing readily available in his laboratory, the fact that Röntgen noticed the effect of his device and the fact that he draw the right conclusion is an excellent example of serendipity, the accidental and unsolicited discovery ^[13]. Serendipitous discoveries abound in science.

Physicists thus gradually discovered the entire spectrum of EM radiation, from radio waves with wavelengths of thousands of kilometers to gamma radiation with wavelengths of 10^-14 meters. Visible light is only a very small part of the full spectrum. The limits left and right of the spectrum in figure 3.11 are not the limits of EM radiation. There is no known absolute upper or lower limit of the EM spectrum.

Figure 3.11: The EM-spectrum. Source: biology.stackexchange.com

To the left of the gamma radiation and to the right of the radio waves the EM-spectrum continues infinitely. The limits in figure 3.11 are not fundamental, they represent just the limits of our measuring instruments.