Sources of Radiation sources can be broadly divided

Sources of Radiation sources can be broadly divided into two categories: • Sources of Radiation Natural Man made.

There are three types of natural sources of radiation: Natural Sources Cosmic Radiation Terrestrial Radiation Internal Radiation Exposure from most of these sources is very minimal and therefore does not cause any measurable damage to our bodies. Q. What are the natural sources of radiation?

Cosmic Radiation Sources Cosmic Radiation is the radiation that comes from variety of sources such as • burning (for example, our Sun) and exploding (for example, Supernovae) stars in outer space. These bodies produce immense amounts of radiation, some of which reach earth. Cosmic Radiation consist from the following components: • Low energy photons known as cosmic microwave background radiation Ø This radiation is thought to be the remnant of the so called big bang that created this universe Although these photons reach the earth’s surface but due to their low energies, they are not deemed harmful. cosmic particles Apart from photons, there are other particles as well that Ø are constantly being produced in the outer space. Most of them, however, never reach the earth either due to magnetic deflection or the earth’s upper protective atmosphere.

particles, like muons, electrons, and neutrinos these are produced Ø when other cosmic particles interact with atoms in the upper atmosphere. Shower of these particles reach earth’s surface but due to their low energies and low interaction probabilities, they do not pose any significant health hazard. Muons and neutrinos directly produced by luminous objects in space also manage to reach earth due to their low interaction capabilities but are not considered hazardous to health due to their extremely low interaction cross sections. Fortunately the earth’s atmosphere acts as a shield to the worst of these radiations Q. Define the cosmic radiation and state its components?

Terrestrial Radiation Sources The main source of terrestrial radiation is the element uranium and its decay products such as thorium, radium, and radon that found in rocks and soil. Our surroundings, the water we drink, the air we breathe in, and the food we consume, all are contaminated with minute quantities of radiation emitting isotopes. Although these isotopes, in general, are extremely hazardous, they are not supposed to cause any appreciable harm to our bodies except when they are present in higher than normal concentrations. The two isotopes of radon, Rn-222 and Rn-220, and their daughter products are the most commonly found hazardous radioactive elements in our surroundings. The main cause of concern with respect to these α-emitting isotopes is their inhalation or digestion, in which case the short range α-particles continue to cause damage to internal organs that can lead to cancer. Q. Explain the source of terrestrial radiation? Q. Why two radon isotopes Rn-222 and Rn-220 re the most hazardous in our environment?

Internal Radiation Sources Our bodies contain some traces of radioactive elements that expose our tissues to continuous low level radiation. This internal radiation primarily comes from Potassium-40 and Carbon-14 isotopes. Potassium-40 is found in foodstuffs and water we consume as Potassium-40 represent 0. 0011% of stable Potassium. Carbon-14 is created in air as result of interaction between cosmic ray and nitrogen nuclei. However the absorbed dose and the damage to tissues due to this radiation is minimal. Q. “Our bodies contain traces mounts of radioactive elements” explain this sentence?

Man-Made Sources Those sources are made and developing by scientists for specific purposes and generally give off one type of radiation. Common examples of such sources are: Medical x-ray machines, Ø X-ray scanners, Ø Nuclear medicines, Ø Particle acceleratorsØ Nuclear reactorsØ Lasers and, Ø Consumer products (television, smoke detectors, and building materials). Ø Out of all these sources, the ones used in medical diagnostics and therapy expose the public to the most significant amounts of radiation. For example a single chest xray exposes the patient to about 20 mrem of radiation, which is a significant fraction of about 360 mrem of total radiation exposure to general public due to all types of radiation. Q. Draw different examples of man- made sources of radiation?

some radioisotopes that are made in laboratories for specific purposes are given in the following table.

General Properties and Sources of Particles and Waves The interaction of particles with atoms is governed by quantum mechanical processes that depend on the properties of both incident particles and target atoms. These properties include mass, electrical charge, and energy. In order to understand the interaction mechanisms of different particles it is necessary to first familiarize ourselves with their properties. Photonsq A photon represents one quantum of electromagnetic energy and is treated as a fundamental particle in the Standard Model of particle physics. In this model the photon is assumed to have no rest mass (although it is never at rest!). When the photon is traveling in a medium, it slows down due to interaction with the medium and acquires an effective mass. In vacuum, however, it is considered to be massless.

An important property of photons is that they carry momentum even though they have no rest mass. The momentum pγ of a photon with energy E, frequency ν, and wavelength λ is given by,

Sources of Photons The most important sources of photons that have wide applications in various fields are: X-ray MachineØ Synchrotron RadiationØ LASERØ Radioactive Sources Ø X-ray Machine§ Production of x-rays is a relatively simple process in which a high Z target (i. e. an element having large number of protons, such as tungsten or molybdenum) is bombarded by high velocity electrons (see Fig). This results in the production of two types of x-rays: Bremsstrahlung and characteristic x-rays. Q. State the different sources of photons?