Beta Particles And The Gamma Rays example essay topic

Benefits of Radiation Radioactivity is the spontaneous disintegration of atomic nuclei by the emission of subatomic particles called alpha particles and beta particles, or of electromagnetic rays called X rays and gamma rays. The phenomenon was discovered in 1896 by the French physicist Antoine Henri Becquerel when he observed that the element uranium can blacken a photographic plate, although separated from it by glass or black paper. He also observed that the rays that produce the darkening are capable of discharging an electroscope, indicating that the rays possess an electric charge. In 1898 the French chemists Marie Curie and Pierre Curie deduced that radioactivity is a phenomenon associated with atoms, independent of their physical or chemical state. They also deduced that because the uranium-containing ore pitchblende is more intensely radioactive than the uranium salts that were used by Becquerel, other radioactive elements must be in the ore.

They carried through a series of chemical treatments of the pitchblende that resulted in the discovery of two new radioactive elements, polonium and radium. Marie Curie also discovered that the element thorium is radioactive, and in 1899 the radioactive element actinium was discovered by the French chemist Andr Louis Debi erne. In that same year the discovery of the radioactive gas radon was made by the British physicists Ernest Rutherford and Frederick Soddy, who observed it in association with thorium, actinium, and radium. Radioactivity was soon recognized as a more concentrated source of energy than had been known before. The Curies measured the heat associated with the decay of radium and established that 1 g (0.035 oz) of radium gives off about 100 cal of energy every hour.

This heating effect continues hour after hour and year after year, whereas the complete combustion of a gram of coal results in the production of a total of only about 8000 cal o energy. Radioactivity attracted the attention of scientists throughout the world following these early discoveries. In the ensuing decades many aspects of the phenomenon were thoroughly investigated. Rutherford discovered that at least two components are present in the radioactive radiations: alpha particles, which penetrate into aluminum only a few thousandths of a centimeter, and beta particles, which are nearly 100 times more penetrating. Subsequent experiments in which radioactive radiations were subjected to magnetic and electric fields revealed the presence of a third component, gamma rays, which were found to be much more penetrating than beta particles.

In an electric field the path of the beta particles is greatly deflected toward the positive electric pole, that of the alpha particles to a lesser extent toward the negative pole, and gamma rays are not deflected at all. Therefore, the beta particles are negatively charged, the alpha particles are positively charged and are heavier than beta particles, and the gamma rays are uncharged. The discovery that radium decayed to produce radon proved conclusively that radioactive decay is accompanied by a change in the chemical nature of the decaying element. Experiments on the deflection of alpha particles in an electric field showed that the ratio of electric charge to mass of these particles is about twice that of the hydrogen ion. Physicists supposed that the particles could be doubly charged ions of helium. This supposition was proved by Rutherford when he allowed an alpha-emitting substance to decay near an evacuated thin-glass vessel.

The alpha particles were able to penetrate the glass and were then trapped in the vessel, and within a few days the presence of elemental helium was demonstrated by use of a spectroscope. Beta particles were subsequently shown to be electrons, and gamma rays to consist of electromagnetic radiation of the same nature as X rays but of considerably greater energy. One of the benefits of nuclear radiation is Radiology. In medicine, Radiology is the discipline of medical science that uses electromagnetic radiation and ultrasonics for the diagnosis and treatment of injury and disease. Radiology originated with the discovery of X rays by German physicist Wilhelm Conrad Roentgen in 1895. Roentgen was awarded the first Nobel Prize in physics for his work.

Another benefit of nuclear radiation is Magnetic Resonance Imaging (MRI). MRI is a medical diagnostic technique that creates images of the body using the principles of nuclear magnetic resonance. A versatile, powerful, and sensitive tool, MRI can generate thin-section images of any part of the body including the heart, arteries, and veins from any angle and direction, without surgical invasion and in a relatively short period of time. MRI also creates "maps" of biochemical compounds within any cross section of the human body. These maps give basic biomedical and anatomical information that provides new knowledge and may allow early diagnosis of many diseases. MRI is possible in the human body because the body is filled with small biological "magnets", the most abundant and responsive of which is the proton, the nucleus of the hydrogen atom.

The principles of MRI take advantage of the random distribution of protons, which possess fundamental magnetic properties. Once the patient is placed in the cylindrical magnet, the diagnostic process follows three basic steps. First, MRI creates a steady state within the body by placing the body in a steady magnetic field that is 30,000 times stronger than the earth's magnetic field. Then MRI stimulates the body with radio waves to change the steady-state orientation of protons. It then stops the radio waves and "listens" to the body's electromagnetic transmissions at a selected frequency. The transmitted signal is used to construct internal images of the body using principles similar to those developed for computerized axial tomography, or CAT scanners.