Phillipp Lenard in 1900

Phillip Lenard was a Hungarian-German physicist who won the Nobel Prize for Physics in 1905 for his research on cathode rays and the discovery of many of their properties. Subsequent research showed that cathode rays are the actual carriers of electricity that are now known as electrons. The fact that the cathode, i.e. the negative electrode, emits the rays showed that electrons carry a negative charge. Lenard’s work formed the basis for Karl Braun’s discovery of the cathode ray tube, which is key to the operation television sets, oscilloscopes, and vidicon television cameras. 

In 1880, Leonard studied physics and chemistry in Vienna and in Budapest. In 1883 he studied under the illustrious Robert Bunsen and Hermann von Helmholtz, and obtained his doctoral degree in 1886. He also studied under Heinreich Hertz.

Prior to his work, cathode rays were produced in partially evacuated glass tubes that had metallic electrodes in them, across which a high voltage could be placed. Cathode rays were difficult to study because they were inside sealed glass tubes, difficult to access, and because the rays were in the presence of air molecules. Lenard overcame these problems by devising a method of making small metallic windows in the glass that were thick enough to be able to withstand the pressure differences, but thin enough to allow passage of the rays. Having made a window for the rays, he could pass them out into the laboratory, or, alternatively, into another chamber that was completely evacuated. He was able to conveniently detect the rays and measure their intensity by means of paper sheets coated with phosphorescent materials. These windows have come to be known as Lenard windows.

Lenard observed that the absorption of the rays was proportional to the density of the material they were made to pass through. This appeared to contradict the idea that they were some sort of electromagnetic radiation. He also showed that the rays could pass through some inches of air of a normal density, and appeared to be scattered by it, implying that they must be particles that were even smaller than the molecules in air. He confirmed some of J.J. Thomson's work, which ultimately arrived at the understanding that cathode rays were streams of energetic electrons. In conjunction with his and other earlier experiments on the absorption of the rays in metals, the general realization that electrons were constituent parts of the atom enabled Lenard to claim correctly that atoms are mostly empty space.

As a result of his Crookes tube investigations, he showed that the rays produced by radiating metals in a vacuum with ultraviolet light were similar in many respects to cathode rays. His most important observation was that the energy of the rays was independent of the light intensity, but was greater for shorter wavelengths of light.

These latter observations were explained by Albert Einstein as a quantum effect. This theory predicted that the plot of the cathode ray energy versus the frequency would be a straight line with a slope equal to Planck's constant, h. This was shown to be the case some years later. The photoelectric quantum theory was the work cited when Einstein was awarded the Nobel Prize in Physics. This much embittered Lenard, who became a prominent skeptic of relativity and of Einstein's theories generally.

Lenard was the first person to study the separation of electric charges accompanying the aerodynamic breakup of water drops. This has since been termed the Lenard effect, but it is also known as spray electrification or the waterfall effect. Lenard also conducted studies on the size and shape distributions of raindrops and constructed a novel wind tunnel in which water droplets of various sizes could be held stationary for a few seconds. He was the first to recognize that large raindrops are not tear-shaped, but are rather shaped something like a hamburger bun. 

Lenard was also an extreme nationalist who despised English physics, which he considered as having stolen their ideas from Germany. During the Nazi reign, he was the outspoken proponent of the idea that Germany should rely on "Deutsche Physik" (best translated as "Aryan physics") and ignore what he viewed as the fallacious and even deliberately misleading ideas of "Jewish physics" (by which he meant chiefly the theories of Albert Einstein). An advisor to Adolf Hitler, Lenard became Chief of Aryan Physics under the Nazis.

Sources

• Cleveland, Cutler (Lead Author); Peter Saundry (Topic Editor). 2008. "Lenard, Phillip." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth September 15, 2006; Last revised December 1, 2008; Retrieved April 5, 2009]. 
• Wikipedia Contributors, Phillip Lenard, Wikipedia The Free Encyclopedia, Accessed 5 April 2009.