Cherenkov Effect
The water that surrounds the core of a nuclear reactor often emits a blue glow. That glow is produced by the Cherenkov effect. This phenomenon was discovered in the 1930s by the Russian physicist Pavel Alexeyevich Cherenkov.
Cherenkov was born in the Voronezh region of Russia on July 15, 1904. He graduated from the Voronezh State University in 1928 and, in 1930, was appointed a senior scientific officer at the Lebedev Physical Institute in Moscow. It was at this institute that Cherenkov carried out the elaborate experiments that revealed the cause of the radiation that was eventually given his name.
The Cherenkov phenomenon can be observed when high-energy radiation passes through a transparent material, such as water. It had long been considered a form of luminescence, somewhat similar to the light emitted by certain dyes when they are exposed to light. By means of an ingenious series of experiments, Cherenkov was able to show that such is not the case.
He demonstrated, for example, that "quenching" does not occur with this form of radiation. The term quenching refers to the gradual decrease in light intensity coming from a luminescent object. Cherenkov radiation does not display a quenching effect.
Cherenkov concluded that the radiation was produced when high-speed charged particles pass through a material at a speed that is greater than the speed of light in the material. The effect is similar to that of the sonic boom caused by an airplane when it travels through air faster than does the sound wave it produces.
For all his experimental accomplishments, Cherenkov was unable to provide a theoretical explanation for his discovery. That theory was developed by two Russian colleagues, Ilya Mikhailovich Frank and Igor Evgenevich Tamm, in 1937. Frank was born in St. Petersburg on October 23, 1908. He graduated from Moscow University in 1930 and later worked at the State Optical Institute and at the Physics Institute of the U.S.S.R. In 1944, he became professor at Moscow University.
Tamm was also born in Vladivostok, on July 8, 1895. He graduated from Moscow University in 1918. After teaching at several universities, he accepted a position at the Physics Institute of the U.S.S.R. in 1934. He died in Moscow on April 12, 1971. For their work on the Cherenkov effect, Cherenkov, Frank, and Tamm received the Nobel Prize for physics in 1958.
An important application of this discovery is the Cherenkov counter. Particles with very short lives (less than 10-10 ) seconds) can be detected by these counters. By constructing counters from suitable materials, they can also be used to determine the velocity of these particles.
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