Radiation or Cherenkov Effect is a curious bluish light that is really an electromagnetic type radiation produced by the passage of particles in a medium at speeds higher than those of light in said medium.
The speed of light depends on the medium and reaches its maximum value in a vacuum. It is true that there is a belief that the value of the speed of light cannot be exceeded, in accordance with the Special Theory of Relativity, which establishes the speed of light in a vacuum at 300,000 km/s, but in a medium in the one that is necessarily inferior.
Origins of the study of Cherenkov radiation
In 1934, the Soviet physicist Pável Alekséyevich Cherenkov (sometimes spelled Čerenkov, Cherenkhov, or even Cerenkhov) was conducting experiments related to radioactivity when he observed a curious phenomenon: when a bottle filled with water containing very high alpha or beta radiation was shaken, energy (charged particles, such as helium nuclei or electrons moving very fast), the bottle glowed with a bluish light.
When high-energy electrons travel through water, where the speed of light is “only” 225,000 km/s, an optical effect is created that is the equivalent of the sonic boom effect produced by a jet when it exceeds the speed of the sound in air, but applied to luminescence.
Cherenkov effect in the water of a nuclear reactor.
The Cherenkov effect appears as a blue glow , for example, in pools of water from nuclear reactors and gamma-ray irradiators. In this case the effect is caused by particles coming from the reactor or the irradiator, which travel at speeds higher than those of light in water. This light spreads out through the medium in a cone shape along the path of the charged particle.
Cherenkov radiation only occurs if the particle passing through the medium is electrically charged, such as a proton. For Cherenkov radiation to occur, the medium must be a dielectric.
Cherenkov received the Nobel Prize in Physics in 1958 for his discoveries related to this reaction, it must be made up of atoms or molecules capable of being affected by an electric field. Therefore, a proton traveling through a medium made of neutrons, for example, would not emit Cherenkov radiation.
Utilities and applications of the Cherenkov Effect
The study of these reactions has not remained a simple scientific curiosity, but has given rise to different uses and evolutions of the original studies. Cherenkov telescopes are very precise tools whose aim is to detect high-energy gamma rays , with a speed close to the speed of light, while traveling in a vacuum.
Perhaps the best known is the MAGIC telescope (Major Atmospheric Gamma-Ray Imaging Cherenkov) in Tenerife, which detects very high-energy gamma rays due to the Cherenkov radiation they produce in the atmosphere, although there are others such as VERITAS, CANGAROO-III, MAGIC and HESS to determine where and with what energy cosmic rays are generated and thus be able to understand
better the physics of the cosmos.
The Cherenkov effect is also very useful in particle detectors where the aforementioned radiation is used as a tracer. Particularly in heavy water neutrino detectors such as Super Kamiokande or Super-K, one of the most precise observatories in the world located one kilometer below the surface of Gifu, Japan.
Since by measuring the angle between the radiation (light) and the particle’s path, the speed of the particle can be determined, the effect is used in the Cherenkov counter , a device for detecting very fast particles and determining their speed or for distinguishing between particles with different speeds.