"The Cosmic Engine" Physics Course

Topics: Electron, Sun, Ionizing radiation Pages: 5 (1252 words) Published: August 1, 2013
Cosmic Engine - Research Task

1. Describe how energy can be released from the nuclei of atoms (6)

Most nuclei are stable. Consisting of protons and neutrons, they are unaffected by chemical reactions and have remained the same since they were formed. However, some nuclei are unstable and spontaneously release energy in the form of a Helium nucleus (α Alpha),an electron (β Beta) and γ Gamma rays. These nuclei are known as radioactive and it’s not possible to predict when a particular radioactive nucleus will emit this energy but a large number of materials are said to have a ‘half life’. The half life is the time it takes for half the nuclei to emit their radiation.

1. Describe and compare the nature of emissions from the nuclei of atoms as radiation of alpha α and beta β particles and gamma γ rays in terms of: (6) Ionising power
Penetrating power
Effect of magnetic field
Effect of electric Field
Alpha Particles:
Alpha particles are composed of two protons and two neutrons and have the same nucleus as Helium. It is a very stable particle. Large nuclei such as Americium-241 emit alpha particles. As it emits alpha particles its mass and atomic number decrease, so it changes into a different element. Alpha particles are good ionizers because of their double positive charge, large mass and because they are relatively slow compared to beta particles. They can also cause multiple ionizations within a very small distance. Because alpha particles are highly ionizing, they are unable to penetrate very far through matter and are brought to rest by a few centimeters of air or less than a tenth of a millimeter of living tissue. After traveling through air for a few centimeters, it will capture electrons and become a Helium atom. Because alpha particles possess the charge of two protons, when they move through a magnetic or electric field a force is exerted on them. This force causes them to accelerate and deflect from their original path.

Beta Particles:
Beta particles are fast moving electrons, carrying a singular negative charge. When a neutron spontaneously decays into a proton and electron, the electron is immediately ejected from the nucleus at a high speed creating the Beta particle. Beta particles are much smaller than alpha particles, being only about 1/7200th the mass of them. Beta particles are much less ionizing than alpha particles and generally do less damage for a given amount of energy deposition, but they can penetrate matter further than alpha particles. Where alpha particles can be stopped by a sheet of paper, beta particles can be stopped by a sheet of metal. Negatively charged Beta particles also experience a force when they move through a magnetic or electric field. At the same speed, a Beta particle will experience half the force that an alpha particle does. The incredibly small mass of beta particles compared to alpha particles means that the force has a greater effect on them and causes a much greater deflection. Their paths bend to a much greater extent than alpha particles.

Gamma Rays:
Gamma rays are an electromagnetic radiation with a very high frequency and very short wavelength. The rays could be described in terms of a stream of photons, which are massless particles each traveling in a wave-like pattern and moving at the speed of light.Gamma photons are the most energetic photons in the electromagnetic spectrum. They are emitted from the nucleus of an atom and are also associated with the fission and fusion of an atom and can accompany α and β decays. Gamma rays have a very high ability to penetrate matter and have a low ability to caus ionisation. Gamma rays are not particles and do not possess any electric charge. They are unaffected by electric and magnetic fields, therefore they will move through these fields without deflecting....
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